Unemployment rates, single parent density, and indices of child poverty: their relationship to different categories of child abuse and neglect.

OBJECTIVE: There were two main research questions: First, is there a relationship between rates of child physical abuse, child sexual abuse and child neglect and levels of female and male unemployment, single-parent density and child poverty in the immediately local area; and second, is this relationship different for different categories of abuse and neglect and different categories of deprivation? METHOD: Using archival data--registered cases of abuse and neglect and official data on child population, social worker ratio, unemployment rates, single-parent density, means-tested clothing grants and free school meals for children--a multiple correlational analysis was carried out of the 5,551 referrals and 1,450 registered cases of abuse and neglect in Glasgow, Scotland for the years 1991 through to 1993. RESULTS: Substantial correlations were found with all indices of deprivation but particularly physical abuse with rates of male unemployment. Lower and more variable correlations were found with female unemployment rates. Sexual abuse and neglect rates showed a less consistent relationship with the indices of deprivation. In general male unemployment rates alone accounted for two-thirds of the variance in total abuse and neglect rates, other factors adding little or nothing to this. CONCLUSIONS: The results demonstrate the importance of selecting small and relatively homogeneous areas for this kind of analysis to achieve ecological validity. Male unemployment rates at this level allow for the ranking of areas in terms of priority need.

Role for cyclic adenosine monophosphate in the synergistic interaction between oxytocin and corticotrophin-releasing factor in isolated human gestational myometrium.

OBJECTIVE: We wished to investigate the role of cAMP in the synergistic effect of corticotrophin-releasing factor and oxytocin on human myometrial contractility. DESIGN: Isolated human gestational myometrium obtained from Caesarean sections at term was studied in vitro. Static incubation techniques as well as tension recordings were applied to the tissue obtained. PATIENTS: The subjects were healthy pregnant women undergoing lower segment Caesarean section at term, prior to labour. MEASUREMENTS: Specimens obtained were immediately dissected into small strips and either incubated in multi-well trays (strip weight 2.75 mg) or superfused and used for tension recordings (strip weight 2.00 mg). cAMP accumulation was measured after incubation with oxytocin (0.1-10 nM), corticotrophin-releasing factor (1 nM) or a combination of both peptides. Tension generated by the muscle strips was recorded isometrically and response to oxytocin (0.01-10 nM), corticotrophin-releasing factor (1 nM) and forskolin (10 nM) expressed in force per gram wet tissue (N/g). RESULTS: Oxytocin (0.1 nM) causes a statistically significant dose-related decrease in cAMP when combined with 1 nM corticotrophin-releasing factor (P less than 0.001), as compared with cAMP stimulation by corticotrophin-releasing factor alone. Time course studies suggest a maximal effect at 1 minute. The hypothesis that an intracellular reduction of cAMP is a prerequisite for the synergistic response in contraction force was tested with tension recordings. Prevention of a decrease in cAMP in the tissue by addition of 10 nM forskolin to the superfusate abolished the potentiation between oxytocin and corticotrophin-releasing factor. CONCLUSIONS: These results indicate that a fall in cAMP concentration plays a vital mediating role in the synergistic interaction between oxytocin and corticotrophin-releasing factor.

Glucocorticoid effects on the molecular forms of adrenocorticotrophic hormone secreted by cultures of rat anterior pituitary cell monolayers.

The effects of glucocorticoids and corticotrophin-releasing factor (CRF) on the release of various molecular forms of adrenocorticotrophic hormone (ACTH) have been investigated in primary cultures of rat anterior pituitary. The rat cells responded to a 30 min challenge with CRF by secreting increased amounts of ACTH, as assessed both by bioassay, using rat adrenocortical cells, and by radioimmunoassay. Inclusion of a synthetic glucocorticoid, such as dexamethasone (DEX), in the incubation for 5 min prior to, and during the CRF challenge, had no effect on the response as measured by radioimmunoassay. Bioassay, however, indicated profound suppression of the response to CRF. This discrepancy between ACTH immuno- and bioactivity was investigated by fractionating the immunoreactive ACTH species using high-performance liquid chromatography. The lower molecular weight (<15kd) forms (ACTH(1-39) , phosphorylated ACTH(1-39) and glycosylated ACTH(1±39) ) were separated from higher molecular weight (>15kd) forms (i.e. ACTH biosynthetic intermediate and proopiomelanocortin) using C-18 Sep-Pak. The lower molecular weight molecules were further resolved into glycosylated and non-glycosylated ACTH, using an acetonitrile gradient high-performance liquid chromatography with trifluoroacetic acid as an ion-pairer. Neither the proportion of low molecular weight forms of ACTH, nor that of glycosylated ACTH(1-39) secreted in response to CRF, were affected by DEX. Further fractionation of non-glycosylated ACTH, also using acetonitrile gradient high-performance liquid chromatography but with heptafluorobutyric acid as the ion-pairer, yielded peaks corresponding to phosphorylated and non-phosphorylated ACTH(1-39) . DEX significantly increased the proportion of phosphorylated ACTH secreted in response to CRF by 18%. An additional effect of DEX was revealed when Sep-Pak extracts were treated with alkaline phosphatase, prior to analysis. After dephosphorylation, it became clear that the peptides released by CRF-stimulated cells were different if DEX was present in the medium. The peptide released in the presence of DEX (ACTH-S) had a slightly, but consistently, different retention time on high-performance liquid chromatography and very little biological activity. Antibody cross-reactivity studies suggested that ACTH-S was modified in the 1-24 region of the peptide. It is concluded that challenge of anterior pituitary cells in primary culture with CRF, following 5 min previous exposure to DEX, results in a molecular change. The consequence of this is that ACTH immunoreactivity is released, but the molecule has reduced biological activity. This may be part of the mechanism by which fast feedback inhibition of ACTH secretion is effected.

Stress responsiveness of hypothalamic corticotrophin-releasing factor and pituitary pro-opiomelanocortin mRNAs following high-dose glucocorticoid treatment and withdrawal in the rat.

In-situ hybridization with synthetic oligonucleotide probes was used to determine the mRNA content of corticotrophin-releasing factor (CRF) and proenkephalin A mRNA in the paraventricular nucleus, and of pro-opiomelanocortin (POMC) mRNA in the anterior pituitary gland of male rats immediately after, and during recovery from, chronic high-dose prednisolone treatment. Levels of transcripts for mRNA for both CRF and POMC were markedly reduced after the treatment, but there was a rapid return to control values for CRF mRNA within 18 h of steroid withdrawal. In untreated animals, the stressful stimulus of i.p. hypertonic saline increased CRF and proenkephalin A mRNA within 4 h with no significant difference in response seen whether the tissues were removed at 13.00 or 20.00 h. The increase in POMC mRNA did not reach statistical significance in these animals. Although prednisolone resulted in a marked reduction of basal CRF mRNA, the stress-induced increment of CRF mRNA remained comparable with that found in untreated animals. On the day following cessation of prednisolone treatment at 09.00 h, basal and stress levels of CRF mRNA were significantly higher in rats killed at 20.00 h than at 13.00 h. Proenkephalin A mRNA transcripts were below quantifiable levels of detection in control or non-stressed prednisolone-treated animals at all the time-points studied. Stress, however, resulted in the accumulation of proenkephalin A mRNA in control animals. This response was inhibited by prednisolone treatment and only returned 18 h after withdrawal. Prednisolone treatment reduced POMC mRNA below the levels detected in untreated animals, with no detectable response to stress.(ABSTRACT TRUNCATED AT 250 WORDS)

Formation of releasable gamma-aminobutyrate from putrescine by rat adrenal slices in vitro.

Rat adrenal gland slices, when incubated in vitro with [1,4-14C]putrescine, accumulate the radioactive diamine and convert it, in part, to a compound indistinguishable (in four separative systems) from [14C]gamma-aminobutyrate (GABA). Adrenal glands taken from animals that had undergone adrenal enucleation 28 days previously, so that the cortex of the tissue had regenerated, likewise formed [14C]GABA from [1,4-14C]putrescine. Putrescine-derived GABA was released from adrenal slices in vitro by 48 mmol K+/l, the release being dependent upon the presence of Ca2+ in the incubation medium. ACTH(1-24) and 8-bromocyclic AMP both provoked a dose-related release of putrescine-derived GABA, although the dose-response curve for the latter differed somewhat from that for the release of corticosterone by this secretogogue. The enzyme believed to be responsible for the first step in the metabolic transformation of putrescine into GABA, diamine oxidase (DAO), is present in extracts of adrenal tissue and its catalytic activity underwent a transient increase followed by a fall below resting levels upon stimulation of adrenal slices with ACTH(1-24). The conclusion that this enzyme initiates the formation of GABA by this pathway is indicated by the observation that adrenal slices pretreated with the DAO inhibitor, aminoguanidine, released significantly less [1,4-14C]putrescine-derived GABA in response to 48 mmol K+/l than did control tissues. The functional significance of these findings remains to be established.

Glucocorticoids act rapidly in vitro to attenuate second messenger responses to ACTH secretagogues in rats.

Fragments of rat anterior pituitary glands incubated in vitro and challenged with either of two ACTH secretagogues were used to investigate the extent to which the acute, biphasic, feedback-like inhibitory effects on hormone secretion exerted by the synthetic glucocorticoid dexamethasone were related to alterations in second messenger responses. Addition of dexamethasone was shown to cause both an immediate inhibition (fast inhibition) of the release of ACTH-like immunoreactivity induced by arginine vasopressin (AVP) or corticotrophin-releasing factor (CRF-41), and also an inhibition that occurred after removal of the steroid and was maximal 90 min after its introduction (early delayed inhibition). The accumulation of adenosine 3',5'-monophosphate (cAMP) in the tissue was enhanced in a dose-related manner by CRF-41, as was that of phosphate esters of inositol (inositol phosphates) by AVP. The dose-response curve for the effect of CRF-41 on cAMP production was markedly shifted to the right by dexamethasone acting in the time-domain of fast inhibition (i.e. the response was attenuated, but not abolished). Application of the steroid during the same time-period reduced significantly the inositol phosphate response induced by the higher concentration of AVP tested (3000 nmol/l), but had no effect on the action of a lower concentration (30 nmol/l). In contrast, the cAMP and inositol phosphate dose-response curves to CRF-41 and AVP respectively were unaffected by the glucocorticoid when it was applied at the time which generated early delayed inhibition of ACTH release.(ABSTRACT TRUNCATED AT 250 WORDS)

Influence of prolonged glucocorticoid treatment on intracellular mechanisms involved in ACTH secretion in the rat.

Two chemically characterized peptides, arginine vasopressin (AVP) and corticotrophin-releasing factor-41 (CRF-41), known to stimulate ACTH secretion by interaction with their respective specific receptors on the corticotroph, were shown to cause the accumulation of phosphate esters of inositol (IP) and adenosine 3',5'-monophosphate (cAMP) respectively when added to rat anterior pituitary fragments incubated in vitro. The former 'second messenger' response (IP production) was unaffected in tissues removed from animals treated with prednisolone in the drinking water (1035 mumol/1) for 14 days. On the other hand, the cAMP response, whilst still present, was inhibited by some 50% in tissues taken from such animals. In contrast, pituitary glands from steroid-treated rats failed to respond to challenge with a variety of substances expected to cause the release of ACTH by mimicking or provoking the production of IP or cAMP. Indeed, of the wide range of ACTH secretagogues tested, only the phospholipase A2 activator melittin was able to cause attenuated ACTH release from tissues removed from treated rats. The failure to provoke ACTH release from tissues removed from steroid-treated animals was also seen when submaximal concentrations of CRF-41 or AVP, or hypothalamic extract or 48 mmol K+/1 were used as the stimuli. The staged recovery of the ACTH secretory response and IP and cAMP accumulation in vitro following the withdrawal of prednisolone treatment was also investigated. A cAMP response that did not differ significantly from that of control tissue and a normal ACTH response to K+ and to melittin were all recovered by 3 days after withdrawal, and the response to cholera toxin showed a partial recovery. Responses to all stimuli of ACTH secretion which cause their effect by entering the corticotrophs were normal by 5 days after withdrawal, when the response to CRF-41 was still significantly, and that to AVP still slightly, reduced compared with controls. Surprisingly, restoration of the ACTH response was most delayed when the expectedly most potent extracellular stimulus (hypothalamic extract) was used. In this case, release was still significantly impaired 7 days after steroid withdrawal. The results show that the glucocorticoid acts to compromise several distinct steps in the process whereby extracellular signals such as CRF-41 and AVP cause the secretion of ACTH. The only step that appears to be spared is the generation of IP by AVP.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of difluoromethylornithine on the LH surge and subsequent ovulation in the rat.

Female Wistar-derived rats with regular oestrous cycles were injected s.c. at 15.00 h on pro-oestrus with difluoromethylornithine (DFMO), a specific inhibitor of ornithine decarboxylase. The drug (10-100 mg/rat) caused a dose-related reduction in the concentration of LH in plasma taken at 19.00 h (the time of the peak of the LH surge in this colony). There was also a dose-related reduction in the pituitary content of total polyamines. The reduction in the plasma concentration of LH was not due to the shifting of the time of the peak of the surge, as concentrations were significantly lower than control from 17.00 to 21.00 h, the overall reduction in total LH release being approximately 50%. The number of ova in the oviducts at 06.00 h next morning was significantly reduced by treatment with 50 mg DFMO/rat, by an average of 70%. Injection of DFMO enhanced the fall in plasma oestradiol concentrations seen between 15.00 and 19.00 h, in a dose-related manner. It also prevented the rise in progesterone concentrations seen in control animals during this period. The ability of DFMO to prevent the rise in plasma concentrations of LH was not secondary to the effects of the drug on ovarian steroid production because DFMO also significantly reduced the LH surge in animals ovariectomized on dioestrus and given appropriate replacement injections of oestradiol and progesterone.(ABSTRACT TRUNCATED AT 250 WORDS)

The combined use of sodium valproate and metyrapone in the treatment of Cushing's syndrome.

We have investigated the combined use of metyrapone and sodium valproate in the treatment of five cases of dexamethasone-suppressible Cushing's disease and one case with dexamethasone non-suppressible disease. Metyrapone alone reduced 24 h urinary free cortisol (UFC) and plasma cortisol concentrations. Addition of sodium valproate to metyrapone produced a further reduction in these values in five of six patients with a reduction in plasma ACTH in three of five patients who had dexamethasone-suppressible disease. Plasma 11-deoxycortisol increased markedly on metyrapone. However, addition of valproate produced a further rise in 11-deoxycortisol values in four of five patients including the patient with dexamethasone non-suppressible disease. The results suggest that valproate may be a useful addition to metyrapone in the medical treatment of some patients with Cushing's syndrome and that it may have an action both at the hypothalamus and peripherally.

The release of luteinizing hormone from pituitaries perifused with thymic extracts.

Medium obtained by the perifusion of fragments of adult male CSE rat thymuses stimulates the release of luteinizing hormone (LH) from the anterior pituitary gland in vitro. The release of the stimulatory factor/s from the thymus appears to be stimulated by the depolarizing concentration of K+ and to be Ca++-dependent. Perifusates from heart, liver and spleen did not elicit the response suggesting that the effect is specific to the thymus gland. Neither LH nor its releasing hormone, LHRH, were detectable in the thymus perifusates by RIA. Levels of facteur thymique serique (FTS), as measured by bioassay are highest in K+ stimulated fractions that exhibit the greatest LH releasing activity. In separate experiments in vitro FTS, but not two other thymic peptides, thymopoietin and thymosin alpha 1, caused a dose-related release of LH from pituitary tissue. That ability of thymic perifusates to cause the release of LH was age-related because tissue from neonatal and ageing males failed to release compounds with any significant effect on the pituitary release of LH. However, when the thymus was enlarged in ageing rats as a result of orchidectomy 1 month before sacrifice LH release was similar to that observed in young male adults.

Permissive role for ornithine decarboxylase and putrescine in the luteinising hormone surge.

Anterior pituitary gland fragments removed from Wistar-derived rats at 10.00 h on pro-oestrus were perifused with Krebs-bicarbonate medium in a column and exposed to hourly volleys of 6 1-min pulses of 10 nM luteinising hormone (LH)-releasing hormone (LHRH). LH release showed a characteristic pattern of prolonged (over 5 h) sensitisation to the releasing hormone, with the response to each volley becoming progressively greater. The addition of 2 mM difluoromethylornithine (DFMO; an inhibitor of ornithine decarboxylase) to the perifusion medium completely inhibited the response to all volleys of LHRH. This effect of DFMO was reversed by the concurrent inclusion of 2 mM putrescine in the medium. Putrescine alone had a small but non-significant enhancing effect on LHRH-induced release, and no significant effect on basal LH release in this system. In a second series of experiments, tissues were loaded with 1-14C-ornithine and the radioactive carbon dioxide released into the medium during the perifusion monitored. Unstimulated pituitary tissues showed constant low levels of carbon dioxide release during 5 h of incubation, but those given hourly volleys of LHRH showed progressively increasing release of radioactivity, which was blocked by the addition of DFMO. No LHRH-stimulated increase in 14CO2 production from 1-14C-ornithine was seen from pituitary tissue removed at 10.00 h on dioestrus. Administration of DFMO (10-100 mg/rat) on the afternoon of pro-oestrus 4 h before the expected peak of the LH surge reduced the magnitude of the subsequent surge and the concentration of the hormone found in the anterior pituitary gland in a dose-related manner. In addition, the concentration of putrescine, but not of spermidine or spermine, was significantly reduced in treated animals (50 mg/rat) at the time of this attenuated surge.(ABSTRACT TRUNCATED AT 250 WORDS)

Prolonged sensitisation of pituitary glands in vitro to repeated administration of luteinising hormone-releasing hormone: effects of pulse frequency, ovariectomy, estradiol and progesterone.

Anterior pituitary gland fragments were obtained from female Wistar-derived rats on dioestrus or pro-oestrus and perifused in Biogel columns in vitro. They were subjected at the beginning of each of 5 h of perifusion to a volley of 6 1-min pulses of luteinising hormone-releasing hormone (LHRH, 10 nM), given 4 min apart. Luteinising hormone (LH) was measured by radioimmunoassay in sequential 2-min fractions of the perifusate. Pituitary glands removed at 14.00 h on dioestrus showed a characteristic pattern of sensitisation followed by desensitisation to the repeated volleys of LHRH, whereas tissues removed at 10.00 or 14.00 h on pro-oestrus showed no evidence of desensitisation over the 5-hour period, the response to each LHRH volley being greater than the preceding one. Estradiol (E, 3-100 pg/ml) added to the medium from the start of perifusion had no significant effect on the pattern of response from tissues removed on pro-oestrus, but the highest concentration significantly enhanced the response of dioestrus pituitaries to all but the last of the LHRH volleys. Progesterone (P, 1-50 ng/ml) added to the medium produced a dose-related inhibition of the response of pro-oestrous tissues to the LHRH volleys. Groups of animals were ovariectomised (OVX) on dioestrus and used for experiment the next morning. OVX at 10.00 h on dioestrus produced the pattern of response characteristic of dioestrus the next morning, but with much higher levels of LH release, which were unaltered by the addition of E to the medium. OVX at 17.00 h on dioestrus produced an entirely different pattern of response the next day, with high basal and moderate LHRH-induced LH release, and no evidence of changes in sensitivity of the tissue.(ABSTRACT TRUNCATED AT 250 WORDS)

Recovery of the components of the hypothalamo-pituitary-adrenocortical axis in the rat after chronic treatment with prednisolone.

Male Wistar-derived rats (200-250 g) were treated for 14 days with prednisolone 21-sodium succinate at a concentration of 1035 mumol/l in their drinking water. The drug was then replaced with normal tap water and groups of animals were killed at various times during recovery, trunk blood being collected after decapitation. At the same time, hypothalamic slices, anterior pituitary gland fragments and adrenals were removed and their responsiveness assessed by exposure to appropriate stimuli in vitro. Tissues were also extracted to measure changes in content of hormones during recovery. Treatment with prednisolone produced marked reductions in body weight gain, adrenal weight and pituitary ACTH content, but no significant change in hypothalamic corticotrophin-releasing factor (CRF) bio- or immunoreactivity. The ACTH content was restored by 5 days after withdrawal but adrenal weight remained significantly reduced after 9 days of recovery. The responsiveness of the hypothalamus to acetylcholine in vitro was markedly inhibited and was still significantly reduced 7 days after withdrawal. The responsiveness of the anterior pituitary gland to synthetic CRF or arginine vasopressin and that of the adrenal gland to ACTH added in vitro were restored simultaneously after 7 days of withdrawal. In vivo, recovery was assessed by measurement of the response to laparotomy stress. Treatment with prednisolone prevented the increase in the plasma concentrations of ACTH and corticosterone produced by stress, and these responses recovered by 5 days (corticosterone) and 7 days (ACTH) after withdrawal. The abolition of the circadian rhythms of ACTH and corticosterone by treatment was also reversed by 5 days after withdrawal.(ABSTRACT TRUNCATED AT 250 WORDS)

The effect of ovine corticotrophin releasing factor (oCRF), bromocriptine and TRH on the secretion of ACTH and alpha-MSH in Nelson's syndrome and Cushing's disease.

The circulating levels of ACTH and alpha-melanocyte stimulating hormone (alpha-MSH) were measured in 9 patients with Nelson's syndrome after the administration of saline, ovine corticotrophin releasing factor (oCRF), bromocriptine or TRH. The concentrations of ACTH were grossly elevated and alpha-MSH levels ranged from undetectable to higher than the normal range. In seven of eight subjects there was a rapid corticotrophic response, but no change in the alpha-MSH level, following oCRF. This response was delayed in one subject. Following oCRF injection, the plasma oCRF profile was variable but circulating oCRF was detectable even at the end of the experiment in all cases. There was no significant change in circulating ACTH or alpha-MSH following either bromocriptine or TRH. Cultured tumour cells from one case of Cushing's disease showed a corticotrophic response but no change in alpha-MSH to oCRF and the response was enhanced by vasopressin. Bromocriptine added to the same tumour depressed ACTH secretion without affecting the output of alpha-MSH. The present data suggest that the tumours in these subjects are responsive to oCRF and arise from corticotrophs rather than melanotrophs.

The combination of 17 alpha-hydroxyprogesterone and 11-epicortisol prevents the delayed feedback effect of natural and synthetic glucocorticoids.

Subcutaneous injection of 400 micrograms/100 g body weight of corticosterone (B) 2 h previously in male rats prevented the stress response, as assessed by the ability of adrenal glands removed from these animals to produce endogenous B. Two injections of a combination of 17 alpha-hydroxyprogesterone and 11-epicortisol, the first given 30 min before and the second with the B, were able to block this inhibitory effect on the stress response. Neither of the steroids alone was effective in this regard. The combination was also effective against the early delayed feedback effects of 400 micrograms/100 g body weight cortisol, prednisolone or beclomethasone dipropionate in the same system. The minimum effective dose for reversal of feedback by B or beclomethasone dipropionate (2 mg/100 g body weight of each antagonist) was lower than that required for the same effect against prednisolone or cortisol (5 mg/100 g body weight). Previous injection of B also abolished the ability of anterior pituitary gland fragments to respond to corticotropin-releasing factors (CRFs) added in vitro, an effect which was not abolished by the injection of the combination of putative antagonistic steroids. From experiments designed to measure the ability of 17 alpha-hydroxyprogesterone and 11-epicortisol to compete with 3H-corticosterone in binding to macromolecular components in hypothalamic, hippocampal and pituitary cytosolic preparations, it was deduced that the competition seen in the hypothalamic and hippocampal, rather than the pituitary, preparations was in better accord with the effect seen on the stress response.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of 6-hydroxydopamine on the hypothalamo-pituitary-adrenocortical axis.

Female rats were treated with two intraventricular injections each of 350 micrograms 6-hydroxydopamine (6-OHDA) and used for experiment 4 or 14 days later. The response to laparotomy, as assessed by subsequent in vitro corticosterone release, was unaffected by the drug, but that to the smaller stress of a skin cut was significantly reduced. Both fast and delayed feedback responses to corticosterone administration were still evident in 6-OHDA-treated animals. When determined 14 days after treatment, hypothalamic concentrations of epinephrine (E) and norepinephrine (NE) were reduced by 46 and 84%, respectively. There was no significant change in content of immunoreactive corticotropin-releasing factor (CRF-41). The acetylcholine-stimulated release of CRF bioactivity from control hypothalami incubated in vitro was significantly inhibited by E or NE, with E being at least 10 times more potent on a molar basis. This effect of NE was enhanced in hypothalami removed from 6-OHDA-treated rats, complete inhibition of acetylcholine-stimulated release of CRF being produced by 0.6 nM NE, as opposed to 6.0 nM for untreated controls. At the level of the anterior pituitary gland, tissue content of adrenocorticotropin (ACTH) was unaffected by treatment, but that of luteinizing hormone (LH) in the same tissues was significantly increased. The corticotrophic response of fragments of the gland incubated or perifused in vitro to hypothalamic extract, CRF-41, arginine vasopressin or E was reduced. In contrast, the response of the tissue to gonadotropin-releasing hormone (GnRH) added in vitro was not significantly affected.(ABSTRACT TRUNCATED AT 250 WORDS)

A correlative study of the binding of dexamethasone in hypothalamic blocks in vitro with its ability to inhibit the release of bioactive corticotrophin-releasing factor.

Rat hypothalamic blocks incubated in vitro were used to study the characteristics of binding of [3H]dexamethasone and other steroids to cytosolic binding sites. Cytosols prepared following incubation of the tissue with [3H]dexamethasone for 2 h contained specifically bound steroid in amounts that depended upon the concentration of potassium (but not sodium) ions in the extracting buffer. There was an increase in bound [3H]dexamethasone extracted as the potassium ion concentration increased up to 0.1 M, but not beyond. Dexamethasone, when added to hypothalami in vitro caused a biphasic inhibition of bioactive corticotrophin-releasing factor (CRF) release, and the extent of the second phase of inhibition was dose-related. 11-Epicortisol, when added in a 100-fold molar excess over dexamethasone was able to prevent the second phase of inhibition caused by the latter steroid, as in the binding studies it was able to cause a 50% reduction in the binding of [3H]dexamethasone. In the functional studies it was shown that 11-epicortisol was able to "rescue" the tissue from dexamethasone-mediated delayed inhibition of CRF secretion if added to the blocks 30 min (but not later) after the agonistic steroid.