Maternal high fructose diet exacerbates white adipose tissue thermogenic process in offspring upon exposure to cold temperature.

AIM: An adverse endogenous environment during early life predisposes to metabolic disorder development. We previously reported adverse metabolic and adipose tissue effects in adult male rats born to dams fed with a fructose-rich diet (FRD). The aim of this work was to determine the effect of a FRD consumed by the pregnant mother on the white adipose tissue (WAT) browning capacity of male offspring at adulthood. MAIN METHODS: Adult SD male offspring from control (C) and FRD-fed mothers were exposed during one week to a cold stimulus. WAT browning capacity was studied through in vivo and in vitro approaches. KEY FINDINGS: After cold exposure, WAT browning was higher in fructose-programmed animals as evidenced by an increase in ucp-1 gene expression, protein levels, and higher UCP-1 positive foci. Moreover, pgc1-α gene expression was increased. In vitro studies showed a lower adipogenic capacity in cells of prenatally fructose-exposed animals differentiated with a white differentiation cocktail, while a higher ucp-1 expression was noted when their cells were treated with a pro-beige differentiation cocktail. SIGNIFICANCE: For the first time we demonstrate that pre-natal fructose exposure predisposes programmed male rats to a higher WAT browning-induced response, under stimulated conditions, despite an apparent lower basal thermogenic capacity. These results should be considered in future studies to generate new therapeutic approaches to deal with adverse programming malnutrition effects.

Testis structure and function in a nongenetic hyperadipose rat model at prepubertal and adult ages.

There are few data for hormonal levels and testis structure and function during postnatal development in rats neonatally treated with monosodium L-glutamate (MSG). In our study, newborn male pups were ip injected with MSG (4 mg/g body weight) every 2 d up to 10 d of age and investigated at prepubertal and adult ages. Plasma levels of leptin, LH, FSH, prolactin, testosterone (T), corticosterone, and free T4 (FT4) were measured. MSG rats displayed elevated circulating levels of corticosterone and hyperadiposity/hyperleptinemia, regardless of the age examined; conversely, circulating prolactin levels were not affected. Moreover, prepubertal MSG rats revealed a significant (P < 0.05) reduction in testis weight and the number of Sertoli (SC) and Leydig cells per testis. Leptin plasma levels were severalfold higher (2.41 vs. 8.07; P < 0.05) in prepubertal MSG rats, and these animals displayed plasma LH, FSH, T, and FT4 levels significantly decreased (P < 0.05). Taken together, these data indicate that testis development, as well as SC and Leydig cell proliferation, were disturbed in prepubertal MSG rats. Adult MSG rats also displayed significantly higher leptin plasma levels (7.26 vs. 27.04; P < 0.05) and lower (P < 0.05) LH and FSH plasma levels. However, T and FT4 plasma levels were normal, and no apparent alterations were observed in testis structure of MSG rats. Only the number of SCs per testis was significantly (P < 0.05) reduced in the adult MSG rats. In conclusion, although early installed hyperadipose/hyperleptinemia phenotype was probably responsible for the reproductive axis damages in MSG animals, it remains to be investigated whether this condition is the main factor for hypothalamus-pituitary-gonadal axis dysfunction in MSG rats.

Angiotensin II and adrenocorticotropin release: mediation by endogenous corticotropin-releasing factor.

Recent reports indicate that the main effect of systemically administered angiotensin II (AII) on ACTH release is probably due to some central nervous system mechanism. The present studies were designed to investigate whether the central action of AII on ACTH release is directly mediated through CRF. In order to test the participation of endogenous CRF in the AII-induced ACTH release in vivo, intact and pharmacologically blocked (pretreated with chlorpromazine-morphine-nembutal) female rats were injected iv with AII (8 nmol/100 g BW). Plasma levels of ACTH as well as CRF content in the median eminence (ME) and medial basal hypothalamus (MBH) were evaluated before and 1, 2.5, and 5 min after treatment. These responses were compared with the effect of 1 min ether exposure on hypothalamic CRF content and plasma ACTH levels in unanesthetized animals. AII injection and ether exposure increased plasma ACTH levels several-fold at both 2.5 and 5 min post treatment in intact rats. Conversely, AII failed to induce any significant increase in plasma ACTH levels in centrally blocked rats at any interval studied. On the other hand, AII injection and ether inhalation acted in similar fashion on CRF content in ME, inducing fast depletion at 1 min post treatment, recovering to control values at 2.5 min after injection, and finally, accumulating peptide at 5 min post treatment. In addition, CRF content in the MBH decreased significantly at 5 min, under both experimental conditions; AII had no effect on hypothalamic CRF content in centrally blocked rats. In vitro experiments using whole MBH (containing ME) fragments incubated with either neural peptides or high K+ solutions indicate that AII possesses a CRF releasing effect at concentrations of 10(-6) M or more. Conversely, other hypothalamic peptides, such as LHRH, TRH, and somatostatin did not induce significant release of CRF at any of the concentrations assayed (10(-7) to 10(-5) M). On the other hand, high K+ solutions released CRF in a concentration-related manner (15-60 mM). These studies suggest that the central effect of AII stimulation on ACTH release in vivo could be, at least in part, through the release of hypothalamic CRF into the portal circulation.

Angiotensin II (AII) and adrenocorticotropin release: modulation by estradiol of the AII biological activity and binding characteristics in anterior pituitary dispersed cells.

The present studies were designed to test if estrogens influence basal and angiotensin II (AII)-stimulated ACTH release and the binding characteristics of AII receptors in isolated anterior pituitary (AP) cells from estrogen-deplete and estrogen-replete rats incubated in vitro. AP cells were obtained from various adult donors: randomly cycling (rc), 10-day ovariectomized (Ovx), Ovx with estradiol restored at a circulating physiological level (Ovx + lEB), Ovx with estradiol at a supraphysiological circulating level (Ovx + hEB); and male (m) rats. The amount of ACTH released under basal conditions was similar in the rc, Ovx + lEB, and m groups, although this amount was significantly greater (P less than 0.02) than that in the Ovx and Ovx + hEB groups. The ACTH-releasing activity (CRA) of AII was concentration dependent (10(-9)-10(-6) M) in all cells. The rank order of the CRA of AII in the groups varied as follows: rc = Ovx + lEB greater than Ovx = Ovx + hEB = m. The slopes of the AII responses were similar. Estradiol addition in vitro did not modify either basal or AII-stimulated ACTH release in any group of cells. AII binding studies indicated that AP cells from donors with different circulating estradiol levels had similar apparent equilibrium dissociation constants (Kd, 16-30 nM). However, the maximum binding capacities in AP cells from the m, Ovx, and Ovx + hEB groups (40, 51, and 49 fmol/10(6) cells, respectively) were significantly lower (P less than 0.05) than those in the rc and Ovx + lEB groups (77 and 81 fmol/10(6) cells, respectively). In summary, these studies indicate that 1) circulating levels of estradiol are able to modulate spontaneous ACTH release by dispersed AP cells; and 2) circulating estradiol, at a lower or higher level than that during the estrous cycle, decreases the in vitro ACTH-releasing activity of AII, possibly through a reduction in the number of AP AII receptors. These results further suggest that estrogen is likely to have a physiological role in corticotropic function.

Arginine vasopressin and adrenocorticotropin release: correlation between binding characteristics and biological activity in anterior pituitary dispersed cells.

The present studies were designed to evaluate the binding characteristics of arginine vasopressin (AVP), using rat anterior pituitary dispersed cells, in correlation with the biological activity of the peptide. Synthetic AVP released ACTH from dispersed anterior pituitary cells in a concentration-dependent fashion, with a minimal effective dose of 10(-10) M. [3H] AVP, the ligand for binding studies, showed full biological activity at different concentrations. Saturable and high affinity binding sites for [3H]AVP were obtained using dispersed anterior pituitary cells. Specific binding reached equilibrium by 180 min at 22 C, and rapid and complete dissociation was obtained after the addition of excess AVP. Scatchard analysis of the data indicated a single class of binding sites, with an apparent Kd of 1.63 nM and a binding capacity (Bmax) of 10.7 fmol/10(6) cells, at 37 C. When cells were incubated at 22 C, Kd (7.63 nM) and Bmax (39 fmol/10(6) cells) values were within the same order of magnitude. AVP effectively inhibited [3H]AVP binding with an IC50 of 1.5 X 10(-7) M, while oxytocin showed a somewhat higher IC50 (0.9 X 10(-6) M) and did not achieve complete inhibition of binding. An AVP analog with a ring substitution ( Asu1 ,6 AVP) showed decreased displacement capacity. Both oxytocin and the AVP analog showed weak ACTH-releasing activity compared to synthetic AVP. This indicates that modifications in the tail and/or ring portion of the AVP molecule reduce both the binding affinity and ACTH-releasing activities of these peptides. Other structurally unrelated peptides with intrinsic ACTH-releasing activity, such as rat corticotropin-releasing factor and angiotensin II, had no affinity for AVP-binding sites. The results indicate that specific AVP-binding sites in anterior pituitary cells are closely correlated with the intrinsic ability of the peptide to elicit ACTH release.

A regulatory loop between the hypothalamo-pituitary-adrenal (HPA) axis and circulating leptin: a physiological role of ACTH.

The product of the ob/ob gene, leptin, is known to be able to exert a modulator, role on HPA axis function. The aim of the present study was to determine whether endogenous ACTH and glucocorticoids exert any regulatory effect on leptin secretion. For this purpose bilaterally adrenalectomized (ADX) or sham operated (Sham) adult male rats were implanted with an indwelling i.v. catheter. A subgroup of ADX animals received, at the same time of surgery, a s.c. corticosterone (B) pellet (75 mg) (ADX+B). All animals were subjected to experimental designs 7 days after surgery. Our results indicate, as expected, that 7-day ADX animals have several fold increased basal ACTH plasma levels and non detectable circulating B, whereas ADX+B rats showed basal plasma ACTH levels in the range of Sham values and plasma B concentrations of about 5 microg/dl. Interestingly, basal plasma leptin levels were significantly (P < 0.05) decreased by 7 days post ADX, and B replacement therapy (ADX+B) restored circulating leptin to Sham levels. Acute dexamethasone (Dxmn, 30 microg/kg body weight, i.v.) treatment induced a very rapid decrease in plasma ACTH concentrations in both Sham and ADX rats, as well as a decrease in plasma B levels in Sham rats. Interestingly, Dxm test had no effect on plasma leptin levels in Sham animals; however, in ADX rats, the synthetic glucocorticoid increased plasma leptin concentrations, restoring the levels observed in Sham rats. This effect occurred at the same time when plasma ACTH levels were decreasing toward basal Sham values. These results clearly indicate that, beside the known effects of leptin on HPA axis function, circulating ACTH and glucocorticoid are able to modulate leptin secretion in plasma. The lack of circulating glucocorticoid and/or increased plasma ACTH concentrations, are responsible for decreasing leptin output, whereas decreased plasma ACTH concentrations allow an increase of leptin secretion in blood. Our data strongly support the existence of a closed, bi-directional, circuit between HPA axis function and adipose tissue metabolism. They further indicate the physiological relevance of different types of stress associated with many phenotypes of obesity.

Increased responsiveness of the hypothalamic-pituitary axis after neurotoxin-induced hypothalamic denervation.

Neonatal treatment with monosodium glutamate (MSG) induces severe neuronal damage in selected brain areas, which in turn results in a number of neuroendocrine abnormalities during adult life. The present study was designed to determine what effects this partial and selective denervation of the hypothalamic-pituitary axis may have on the sensitivity of two key components of that axis, the median eminence (ME) and the anterior pituitary (AP). In order to test any changes in response that may occur after MSG treatment, the release of several peptide hormones from either the ME or the AP was evaluated in vitro, employing specific or general secretagogues. Male newborn pups of the Holtzman strain were injected with MSG every other day for 5 days, starting on day 2 of life; littermate controls received an injection of 10% NaCl. All animals were used when adult, at about 5-7 months of age. After decapitation, ME and AP tissues from control and MSG-treated rats were dissected out and incubated in vitro. Release of LHRH, SRIF, arginine vasopressin, and oxytocin from the ME was measured by direct RIA, under basal conditions and after stimulation with high K+ medium (28 mM). The results clearly indicate a marked hyperresponse of the release of each of the four neuropeptides by ME fragments from MSG-lesioned animals. The altered release was not attributable to changes in ME peptide content. In the case of the AP, the release of ACTH, LH, PRL, and GH in response to high K+ or, in some cases, to specific releasing factors, was evaluated in a dispersed cell preparation. The release of all four protein hormones was increased by high K+, and again the MSG-lesioned rats showed a pronounced hyperresponse. Corticotropin-releasing factor, at concentrations of 10(-9) and 10(-8) M enhanced ACTH release from control and MSG-lesioned rats, but the latter presented a marked hyperresponse. A similar observation on LH release was seen after stimulation with LHRH (10(-9) M). The results indicate that the neuronal damage induced by neonatal MSG treatment results in a generalized hyperresponsiveness in vitro to either specific or general secretagogues by ME or AP tissues, which may suggest the development of a denervation-type supersensitivity in the hypothalamic-pituitary axis. Since the release of these peptide hormones is sluggish in MSG-lesioned rats under in vivo conditions, it seems plausible to conclude that the major defect after the neurotoxin damage may reside in the loss of neurotransmitter systems normally innervating and regulating the activity of the peptidergic neurons.

Role of central epinephrine on the regulation of corticotropin-releasing factor and adrenocorticotropin secretion.

Epinephrine (EPI) has been described to stimulate the hypothalamic-pituitary-adrenal axis. However, whether central EPI neuronal systems play a major physiological role in the regulation of ACTH secretion and whether that role is primarily stimulatory or inhibitory in nature is still controversial. The present study addressed these questions using different inhibitors of phenylethanolamine-N-methyltransferase (PNMT), which were either active peripherally or were both peripherally and centrally active. Male rats received either vehicle or a PNMT inhibitor at various times before further experimental procedures. A large decrease in hypothalamic EPI levels was observed in rats given central PNMT inhibitors, whereas these treatments did not affect hypothalamic norepinephrine (NE) levels. Plasma EPI, but not NE, was decreased to similar levels after treatment with peripheral or central PNMT inhibitors. Basal plasma ACTH decreased slightly during the 12 h after central PNMT inhibition. Central, but not peripheral, inhibition of PNMT significantly decreased the plasma ACTH response to ether vapor stress at 5 and 15 min. This effect was seen 3 or 12 h after PNMT inhibition. The suppression of the stress response was not due to a change in responsiveness of the pituitary to CRF. The hypothalamic content of CRF was significantly decreased 9 and 12 h after inhibition of central PNMT. Blockade of the stress response actually preceded the changes in CRF levels. The content of arginine vasopressin, another potent ACTH secretagogue, was not affected 3, 6, 9, or 12 h after that treatment. The effect on CRF was not observed in rats treated with the peripheral PNMT inhibitor, nor was it caused by manipulation and stress of the animals 12 h before death. The dat demonstrate that central inhibition of PNMT, which produces a selective decrease in hypothalamic EPI levels, blunts the response of plasma ACTH to ether vapor stress, and at later times also causes a selective decrease in CRF content. Furthermore, the altered ACTH response to ether stress is not due to a change in responsiveness of the pituitary to CRF or to an alteration in arginine vasopressin levels. Thus, an endogenous EPI neuronal system appears to stimulate CRF neurons responsible for the increase in ACTH after ether vapor stress.

Effects of gonadectomy and sex hormone therapy on the endotoxin-stimulated hypothalamo-pituitary-adrenal axis: evidence for a neuroendocrine-immunological sexual dimorphism.

Bacterial lipopolysaccharide (LPS) stimulates the hypothalamo-pituitary-adrenal axis by a mechanism involving the release of cytokines, which activate the CRH-ACTH system and, as a result, increase glucocorticoid secretion. In the present study we investigated the possibility that endogenous sex hormones modulate the in vivo endotoxin-stimulated adrenal and immune responses in adult BALB/c mice. In preliminary experiments we determined that the maximal glucocorticoid release in response to LPS (50 micrograms, ip) administration was reached 2 h after treatment. The endotoxin effect on the adrenal and immune responses was then tested in male, randomly cycling female, 20-day-gonadectomized and 20-day-gonadectomized mice treated with either testosterone or estradiol. In addition, in vitro experiments were performed to determine whether 1) LPS exerts any direct effect on basal and ACTH-stimulated corticosterone release, and 2) adrenal function is influenced by bilateral gonadectomy and sex steroid therapy. Our results indicate that 1) randomly cycling female mice have significantly more pronounced corticosterone secretion than males 2 h after endotoxin injection, although the tumor necrosis factor responses were similar; 2) the response of the hypothalamo-pituitary-adrenal axis to endotoxin stimulation in female mice was invariable throughout the different stages of the normal estrous cycle; 3) gonadectomy leads to enhanced (P < 0.05) adrenal and immune responses to LPS stimulation compared to the responses in shams; 4) the endotoxin-elicited adrenal and immune overresponses observed in gonadectomized mice are reversed by testosterone treatment, regardless of sex; 5) LPS does not directly modify spontaneous and ACTH-stimulated adrenal corticosterone secretion; and 6) gonadectomy alone or combined with sex steroid therapy does not increase the in vitro adrenal response to ACTH stimulation. Our findings further suggest an evident neuroendocrine-immunological sexual dimorphism during the acute phase of inflammatory processes.

A phospholipase A2-related snake venom (from Crotalus durissus terrificus) stimulates neuroendocrine and immune functions: determination of different sites of action.

Immune neuroendocrine interactions are vital for the individual's survival in certain physiopathological conditions, such as sepsis and tissular injury. It is known that several animal venoms, such as those from different snakes, are potent neurotoxic compounds and that their main component is a specific phospholipase A type 2 (PLA2). It has been described recently that the venom from Crotalus durissus terrificus [snake venom (SV), in the present study] possesses some cytotoxic effect in different in vitro and in vivo animal models. In the present study, we investigated whether SV and its main component, PLA2 (obtained from the same source), are able to stimulate both immune and neuroendocrine functions in mice, thus characterizing this type of neurotoxic shock. For this purpose, several in vivo and in vitro designs were used to further determine the sites of action of SV-PLA2 on the hypothalamo-pituitary-adrenal (HPA) axis function and on the release of the pathognomonic cytokine, tumor necrosis factor alpha (TNF alpha), of different types of inflammatory stress. Our results indicate that SV (25 microg/animal) and PLA2 (5 microg/animal), from the same origin, stimulate the HPA and immune axes when administered (i.p.) to adult mice; both preparations were able to enhance plasma glucose, ACTH, corticosterone (B), and TNF alpha plasma levels in a time-related fashion. SV was found to activate CRH- and arginine vasopressin-ergic functions in vivo and, in vitro, SV and PLA2 induced a concentration-related (0.05-10 microg/ml) effect on the release of both neuropeptides. SV also was effective in changing anterior pituitary ACTH and adrenal B contents, also in a time-dependent fashion. Direct effects of SV and PLA2 on anterior pituitary ACTH secretion also were found to function in a concentration-related fashion (0.001-1 microg/ml), and the direct corticotropin-releasing activity of PLA2 was additive to those of CRH and arginine vasopressin; the corticotropin-releasing activity of both SV and PLA2 were partially reversed by the specific PLA2 inhibitor, manoalide. On the other hand, neither preparation was able to directly modify spontaneous and ACTH-stimulated adrenal B output. The stimulatory effect of SV and PLA2 on in vivo TNF alpha release was confirmed by in vitro experiments on peripheral mononuclear cells; in fact, both PLA2 (0.001-1 microg/ml) and SV (0.1-10 microg/ml), as well as concavalin A (1-100 microg/ml), were able to stimulate TNF alpha output in the incubation medium. Our results clearly indicate that PLA2-dependent mechanisms are responsible for several symptoms of inflammatory stress induced during neurotoxemia. In fact, we found that this particular PLA2-related SV is able to stimulate both HPA axis and immune functions during the acute phase response of the inflammatory processes.

Cytokines, leptin, and the hypothalamo-pituitary-adrenal axis.

The endocrine and immune systems are linked via an elaborated communication system constituted by an array of cytokines and neuropeptides which interact to modulate the integrated response of an organism to infection. Weight loss and anorexia, probably secondary to cytokine release, frequently accompany infection, but leptin could also play a role. Like cytokines, leptin serves as a peripheral messenger to convey signals to the brain. Expression of leptin is stimulated by glucocorticoids, endotoxins, and cytokines; on the other hand, leptin seems to inhibit the activation of the hypothalmo-pituitary-adrenal (HPA) axis. Indeed leptin exerts a direct, dose-dependent inhibition of stimulated cortisol secretion by normal human and rat adrenal cells in vitro. These effects are mediated by the long isoform of the leptin receptor, because its transcript is expressed in the adrenal tissue. In addition we investigated the role played by the glucocorticoids in the development of tolerance of the hypothalamo-corticotropic, immune and adipose system responses to repeated endotoxin administration. Unlike that of the corticotropic axis, tolerance of the immune and adipose systems is at least partially glucocorticoid-independent. This crosstalk between the endocrine, immune, and adipose systems may be of prime importance to homeostasis in pathophysiological events occurring during infection.

The hypothalamo-pituitary-adrenal axis of athymic Swiss nude mice. The implications of T lymphocytes in the ACTH release from immune cells.

Because of the well-known role of the thymus in the regulation of immune function, we investigated whether the lack of thymus may affect hypothalamo-pituitary-adrenal (HPA) axis activity. Eight-week-old female Swiss nude (athymic) and BALB/c (normal) mice were used to study (a) the "in vivo" response of the HPA axis to various stresses and stimuli acting at either hypothalamic, pituitary, or adrenal levels and (b) the "in vitro" response of pituitary and adrenal cells to CRH and ACTH stimulation, respectively. The results indicate that (1) basal plasma ACTH levels were significantly (p < 0.05) higher in Swiss nude than in BALB/c mice, whereas basal corticosterone (B) levels were similar in both strains of mice; (2) the stress-induced release of ACTH and B in plasma was significantly (p < 0.05) lower in Swiss nude than in BALB/c mice, regardless of the stimulus applied; (3) the "in vitro" pituitary response to CRH and the adrenal response to ACTH were significantly (p < 0.05) lower in Swiss nude than in BALB/c mice; and (4) whereas hypothalamic CRH and pituitary ACTH contents were similar in both strains, adrenal B content was significantly (p < 0.05) lower in athymic mice. Immune reconstitution of the athymic nude mice by injecting splenocytes obtained from syngeneic heterozygous (i.e., immunologically fully competent) donors produced a significant increase in the B adrenal content of the nude mice. Among the splenocytes, CD4+ T-lymphocytes play a particularly important role in the release of ACTH from cells of the immune system. In conclusion, our results indicate that athymic nude mice have a blunted HPA axis response to various stresses and stimuli; this defect seems to reside at both the pituitary and adrenal levels. Immune reconstitution of the nude mice leads to a normalization of the adrenal B content.

Effects of neonatal monosodium glutamate (MSG) treatment on the hormonal and central monoaminergic dynamics associated with acute ether stress in the male rat.

Neonatal treatment with monosodium glutamate (MSG) induces severe neurochemical damage to several brain regions, and these lesions are expressed in adult life by a variety of endocrine and behavioral abnormalities. The present study analyzes the extent of the neurochemical damage to several monoaminergic systems by evaluating the changes in norepinephrine (NE), dopamine (DA), and 5-hydroxytryptamine (5-HT) metabolism induced by the neurotoxin in several discrete hypothalamic loci. Moreover, the study also evaluated the ability of MSG-treated rats to respond to acute ether stress, by measuring the release of ACTH and prolactin induced by ether and correlating those changes with the alterations in monoamine metabolism in the arcuate (AN), dorsomedial (DMN), and suprachiasmatic (SCN) nuclei and in the median eminence (ME). The results indicate that MSG treatment induces marked changes in monoamine metabolism in several of the regions examined. The metabolite of DA, dihydroxyphenylacetic acid, was markedly depressed in the AN, SCN, and DMN. NE metabolism was also significantly lower in the AN of MSG-treated animals. 5-HT metabolism was also altered by MSG treatment, with significant decrements recorded in the SCN, DMN, and AN. Both control and MSG-treated rats showed highly significant increments in ACTH and PRL release 5 and 15 min after exposure to ether vapors. The only quantitative difference between the two groups was a smaller increment in ACTH levels 5 min after ether in the MSG group. Ether stress increased DA metabolism in the AN, NE metabolism in the AN and DMN, and 5-HT metabolism in the SCN in control animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiotensin II increases ACTH release in the absence of endogenous arginine-vasopressin.

Recent studies from our laboratory indicate a primary central site of action of Angiotensin II (AII) to release ACTH. The present studies were designed to test whether AII is able to release ACTH in vivo in a similar fashion in intact, cannulated, freely moving Long-Evans (LE) or in vasopressin (AVP)-deficient, Brattleboro (DI) female rats. The in vivo response to AII was compared with that elicited by synthetic CRF. AII injected i.v. (0.4 or 2 micrograms/100 g BW) induced a significant, dose-related increase in plasma ACTH values 5 and 15 min after injection, in both LE and DI rats. CRF given to LE and DI rats at 0.4 micrograms/100 g BW elicited a larger increase in ACTH plasma values than a similar dose of AII, 5 or 15 min after the injection. Moreover, ACTH levels after CRF in DI rats were significantly greater than those obtained in LE controls. In vitro studies using dispersed anterior pituitary cells indicate that the response of cells from either LE or DI rats to AII or AVP (both at 10(-9) and 10(-8)M) was similar. Cells from DI donors were hyperresponsive to CRF (2 X 10(-11) and 10(-10)M) in terms of ACTH release when compared with the response of cells from LE rats. The present results suggest that the presence of AVP is not essential to mediate the central response to AII and that AII may act centrally to stimulate CRF release from the hypothalamus in vivo, which would then enhance ACTH output. The results in the DI rat indicate that the increased response to CRF may be an important compensatory mechanism involved in the regulation of adrenocortical function in the DI rat.

Sex- and stress-steroids interactions and the immune system: evidence for a neuroendocrine-immunological sexual dimorphism.

It is well established that sexual dimorphism exits within the immune system. Females have higher levels of immunoglobulins, greater antibody response to antigens, and higher incidence of autoimmune diseases, such as systemic lupus erythematosus, Grave's disease, and Hashimoto thyroiditis than males. Spontaneous autoimmune syndromes in mice are more prevalent and of greater severity in females compared with males, and the course of the disease can be modulated by changes in levels of gonadal steroids. A sexual dimorphism is also present in the pituitary-adrenal function: females have higher corticosterone levels and higher corticosteroidogenesis. In the context of the immune-neuroendocrine interactions, we investigated the effects of gonadectomy and sex hormone therapy on endotoxin-stimulated hypothalamo-pituitary-adrenal axis. Whereas endotoxin-induced corticosterone release is invariable throughout the different stages of the oestrus cycle, gonadectomy in both male and female mice leads to enhanced adrenal and immune responses to endotoxin. Interestingly, these enhanced adrenal and immune responses can be completely reversed by testosterone treatment regardless of the sex of the mice. Studies performed over development confirm the role of endogenous testosterone in modulating the endotoxin-induced corticosterone secretion. Indeed, corticosterone response to endotoxin is maximal before puberty when endogenous testosterone levels are low and declines in postpubertal and adult mice. In conclusion, all these data support a sex steroid hormone basis for a neuroendocrine-immunologic sexual dimorphism.

Participation of the central serotonergic pathway in the endotoxin-stimulated hypothalamo-pituitary-adrenal axis function.

The aim of the present study was to determine whether the central serotoninergic pathway (5HT) plays any stimulatory/inhibitory role in endotoxin-stimulated hypothalamo-pituitary-adrenal (HPA) axis function in the male rat. For this purpose, animals inhibited or not of central 5HT synthesis were injected with vehicle alone or containing endotoxin (LPS) and killed 2 h later. The results indicate that the inhibition of the 5HT pathway did not modify the LPS-induced hypoglycemia but that it significantly reduced ACTH release in plasma. Although the inhibition of 5HT did not modify the CRH-ergic system, it diminished hypothalamic vasopressin (AVP) content in basal condition. After LPS injection, rats inhibited of 5HT synthesis showed a significant activation of the hypothalamic AVP-ergic system whereas control rats did not. These data clearly indicate that decreased HPA axis function after 5HT inhibition could be partially compensated by the facilitation of the AVP neuronal activity.

Circulating and mitogen-induced tumor necrosis factor (TNF) in malnourished children.

Malnutrition in children is associated with an increased risk of infection and death. Multiple abnormalities in the inflammatory-immune response, including cytokine production, have been described in protein energy malnourished (PEM) children and could account for increased severity and frequency of infection. The aim of the present study was to determine whether there are abnormal basal tumor necrosis factor (TNF) serum concentrations in PEM children, to relate it with serum cortisol and plasma corticotrophin levels and to explore simultaneously the in vitro production of TNF by peripheral blood leukocytes (PBL). No differences were found in basal plasma corticotrophin and serum cortisol concentrations in malnourished as compared with normal, well-nourished control children. Basal TNF serum concentrations were significantly higher in malnourished children than in controls. Conversely, mitogen induced TNF production by PBL in vitro was significantly reduced in PEM children compared with controls. Abnormalities in circulating and mitogen-induced TNF production are present in malnourished children even in absence of elevated serum cortisol concentrations. These abnormalities potentially could modify inflammatory-immune responses to infectious stimuli in malnourished children.

[Role of nitric oxide in alterations of the systemic and splanchnic hemodynamics in a experimental model of portal hypertension]. / Papel del óxido nítrico en las alteraciones de la hemodinámica sistémica y esplácnica en un modelo experimental de hipertensión portal.

Recent experimental studies have suggested that an increase in the synthesis of nitric oxide, a powerful vasodilator secreted by endothelial cells, plays a role in the hemodynamic disturbances associated to portal hypertension. The present study was addressed to investigate the effects of L-NNA (a specific inhibitor of nitric oxide) on systemic and splanchnic hemodynamics in portal hypertensive rats, induced by partial portal vein ligation. Intravenous infusion of L-NNA (50 ug/kg/min) significantly increased systemic blood pressure and decreased cardiac output as measured by radiolabeled microspheres. A significant increase in systemic and splanchnic vascular resistance was also observed in L-NNA-treated rats; whereas portal blood flow decreased significantly, L-NNA did not modify portal pressure. Pretreatment with L-arginine (300 mg/Kg, i.v.) prevented the hemodynamic changes induced by L-NNA. Similar values of endotoxin levels were detected in both groups of animals. In the control group, L-NNA caused a mild but significant increase of mean arterial pressure; no significant changes on the other hemodynamic parameters were observed. These results suggest that an increase in endogenous synthesis of nitric oxide may play an important role in hemodynamic disturbances associated with chronic portal hypertension.