Prolactin receptor content of rabbit milk.

Rabbit milk fat globule membranes have been shown to contain PRL receptors by a variety of criteria, including hormonal specificity and inhibition by specific anti-PRL receptor antisera. Collection of milk samples throughout the period of lactation facilitated a temporal study of the receptor content of the membrane fraction of these milk samples by Scatchard analysis after treatment with 5 M MgCl2 to dissociate endogenously bound PRL. Total receptor content was low after parturition (3.3 +/- 1.3 fmol/mg membrane protein) but increased subsequently, reaching maximal levels (43.7 +/- 3.4 fmol/mg) by day 21 of lactation. No significant difference in the Ka (4.9 X 10(9) +/- 0.35 M-1) of the milk receptor was detected over a 4-week suckling period. No apparent relation seemed to exist between rabbit serum PRL values measured by RIA in serum samples taken just before milking and milk PRL receptor content. Milk receptor content, however, was significantly (P < 0.02) correlated with the PRL receptor content of the gland when animals were sacrificed immediately after milking.

Effects of hyperthyroidism and hypothyroidism on rat growth hormone release induced by thyrotropin-releasing hormone.

The effect of synthetic thyrotropin-releasing hormone (TRH) on the release of growth hormone (GH) and thyroid-stimulating hormone (TSH) was investigated in euthyroid, hypothyroid, and hyperthyroid rats under urethane anesthesia. In euthyroid control rats, intravenous injection of TRH (200 ng/100 g BW) resulted in a significant increase in both plasma GH and TSH. In rats made hypothyroid by treatment with propylthiouracil or by thyroidectomy, basal GH and TSH levels were significantly elevated with exaggerated responses to TRH. In contrast, plasma GH and TSH responses to TRH were both significantly inhibited in rats made hyperthyroid by L-thyroxine (T4) treatment. These results suggest that altered thyroid status influences GH release as well as TSH secretion induced by TRH in rats.

Stimulating and inhibiting effects of thyrotropin-releasing hormone on growth hormone release in rats.

The effect of thyrotropin-releasing hormone (TRH) on the mechanism regulating growth hormone (GH) secretion was investigated in urethane-anesthetized male rats. The iv injection of TRH (0.2 and 3 mug/100 g BW) caused a significant and dose-related increase in plasma GH. Greater GH responses to TRH were not obtained with doses of TRH larger than 5 mug/100 g BW. TRH injection also raised plasma GH in rats subjected to hypothalamic ablation, in which the maximum increments of plasma GH after TRH injection were greater than in control rats. Plasma GH responses to the iv injection of chlorpromazine (200 mug/100 g BW) were significantly augmented by the concomitant iv injection of TRH in a dose of 3 mug/100 g BW. However, a large dose of TRH (25 mug/100 g BW) injected with chlorpromazine caused a significantly smaller increase in plasma GH than did smaller doses of TRH (0.2 and 3 mug/100 g BW). TRH injection into the lateral ventricle (0.02 and 0.2 mug/100 g BW) inhibited significantly the GH release induced by chlorpromazine, whereas TRH (0.2 mug/100 g BW) alone caused only a slight increase in plasma GH. These results suggest that TRH may not only stimulate GH release by a direct action on the pituitary, but may also modify GH secretion by acting through the central nervous system.

Effects of indoleamines and their newly identified metabolites on prolactin release in rats.

Plasma immunoreactive PRL responses to indoleamines and their metabolites were studied in urethane-anesthetized rats. All drugs were injected into the lateral ventricle and blood samples were serially collected from a jugular vein. Serotonin and melatonin caused a significant increase in plasma PRL with peak values at 10-20 min after the injection. Significant increase in plasma PRL were also observed after the administration of 5-hydroxykynurenamine (5-HK), a newly identified serotonin metabolite. The potency of 5-HK was less than that of serotonin but much greater than that of melatonin. In contrast, plasma PRL did not change significantly in response to N-acetyl-5-methoxykynurenamine, another newly identified metabolite of melatonin, or a vehicle solution. Simultaneous administration of melatonin significantly blunted the plasma PRL response to serotonin, whereas the rise in plasma PRL induced by 5-HK was not blunted by melatonin. These results suggest that indoleamines as well as their metabolites play a role in regulating PRL secretion in rats.

Suppression by thyrotropin-releasing hormone (TRH) of growth hormone release induced by arginine and insulin-induced hypoglycemia in man.

Plasma growth hormone (GH) levels were significantly increased following L-arginine (30 g) infusion or insulin (0.1 U/kg body wt)-induced hypoglycemia in normal men. When synthetic thyrotropin-releasing hormone (TRH) (1 mg) was infused intravenously for 150 min, beginning 30 min before arginine or insulin administration, GH responses to arginine and insulin were significantly blunted with a mean (+/- SE) percentage inhibition of 80.1 +/- 8.8% and 30.6 +/- 10.3%, respectively. These results suggest a possible inhibitory effect of TRH on GH secretion in man.

Growth hormone and prolactin release after injection of thyrotropin-releasing hormone in patients with depression.

The effects of thyrotropin-releasing hormone (TRH) on the release of growth hormone (GH), prolactin (PRL) and thyrotropin (TSH) were investigated in patients with depression. Intravenous injection of synthetic TRH (500 mug) caused a significant increase in plasma GH (peak value: 7.7 minus 35.0 ng/ml) in 8 of 13 patients with mental depression. After clinical recovery these patients had no response of plasma GH to TRH. TRH administration did not raise plasma GH in normal subjects examined. Plasma PRL responses to TRH were significantly enchanced (P smaller than 0.05) in depressed patients compared with control subjects. Plasma TSH responses to TRH were significantly blunted in patients with depression (P smaller than 0.05). These results suggest disorders in the hypothalamo-pituitary function in depression.

Effects of water deprivation and administration of hypertonic saline on dopamine concentrations in posterior pituitary and vasopressin release in rats.

Changes in concentrations of arginine vasopressin (AVP) in plasma and the neurointermediate lobe of the pituitary and those in dopamine (DA) in the neurointermediate lobe in rats were studied simultaneously after depriving the animals of water as well as after giving intraperitoneal (i.p.) injections of hypertonic saline (4.5% saline, 25 ml/kg of body weight). After water deprivation for 24 h, both AVP in plasma and DA in the neurointermediate lobe increased without any changes in AVP in the neurointermediate lobe. Water deprivation for 48-72 h caused further increases in both AVP in plasma and DA in the neurointermediate lobe with a significant decrease in AVP in the neurointermediate lobe. Rehydration for 24 h subsequent to 72 h of water deprivation made AVP in plasma and DA in the neurointermediate lobe return to the values of normally hydrated rats, whereas AVP in the neurointermediate lobe was still depressed. Thirty min after the i.p. injection of hypertonic saline, both AVP in plasma and DA in the neurointermediate lobe increased markedly with no change in AVP in the neurointermediate lobe. The time course of change in DA in the neurointermediate lobe was similar to that in plasma AVP when plasma osmolality was changed chronically or acutely. These results may make questionable the preconception that the tuberohypophyseal DA neurons are not involved in or regulated by early changes in vasopressin secretion.

Interleukin-1 (IL-1) stimulates the release of corticotropin-releasing factor (CRF) from superfused rat hypothalamo-neurohypophyseal complexes (HNC) independently of the histaminergic mechanism.

We demonstrated previously that interleukin-1 (IL-1) (recombinant human IL-1 alpha and -1 beta) stimulated the release of corticotropin-releasing factor (CRF) from the superfused rat hypothalamo-neurohypophyseal complex (HNC), independently of the cholinergic system. In the present study we studied the effects of IL-1 on the release of CRF not only from the HNC but also from the isolated hypothalamus of rats in a superfusion system to define the origin of measured CRF and the site of IL-1 action. We also studied the possible involvement of the histaminergic system in the mediation of the stimulation by IL-1. An increase in CRF was elicited from the HNC and the isolated hypothalamus in a dose-dependent manner by human recombinant IL-1 beta in concentrations of 0.1-10 nM with similar time courses. Histamine in concentrations of 1-100 nM also elicited qualitatively similar increases of CRF from these two types of explants. The increases in CRF release from the HNC induced by 10 nM of histamine were completely suppressed in the combined presence of pyrilamine (10 microM) and cimetidine (10 microM), an H1 and an H2 receptor antagonist, respectively. On the other hand, the increase in CRF release induced by 10 nM IL-1 beta was not affected by the combination of these two antagonists. These results indicate that IL-1 stimulates CRF release from the median eminence through an action on the hypothalamus, and that the stimulatory effect of IL-1 is probably independent of the histaminergic system.

Interleukin-1 (IL-1) stimulates arginine vasopressin (AVP) release from superfused rat hypothalamo-neurohypophyseal complexes independently of cholinergic mechanism.

We studied whether interleukin-1 (IL-1) affects the release of arginine vasopressin (AVP) from the superfused hypothalamo-neurohypophyseal complex (HNC) of rats. Involvement of the cholinergic system in the mediation of IL-1 on AVP release from HNC was also examined. Both human recombinant IL-1 alpha and -1 beta elicited a rapid increase of AVP from HNC in a dose-dependent manner at concentrations ranging from 0.1 to 10 nM. However, neither IL-1 alpha nor -1 beta at concentrations of 100 nM increased AVP, and even suppressed the stimulatory effect of 10 nM IL-1 alpha and -1 beta added later. Acetylcholine at concentrations of 1 to 100 nM caused a dose-dependent, rapid increase in AVP, whereas AVP release induced by 10 nM acetylcholine was completely suppressed by the combined presence of 10 microM hexamethonium, a nicotinic receptor antagonist, and 50 microM atropine, a muscarinic receptor antagonist. On the other hand, AVP release induced by 10 nM IL-1 alpha and -1 beta was not affected by the combination of the two antagonists. These results suggest that both IL-1 alpha and -1 beta may stimulate AVP release by acting directly on the hypothalamo-neurohypophyseal system, and that the stimulatory effect of IL-1 on AVP release may be independent of the cholinergic system.

Stimulation of cholecystokinin (CCK) release from superfused rat hypothalamo-neurohypophyseal complexes by interleukin-1 (IL-1).

This in vitro study examined the effects of interleukin-1 (IL-1) and interferon-gamma (Ifn-gamma) on the release of cholecysto-kinin (CCK) from superfused hypothalamo-neurohypophyseal complexes (HNC) of rats. An increase of CCK from HNC was elicited in a dose-dependent manner by recombinant human IL-1 alpha and -1 beta in concentrations of 0.1-10 nM. In contrast, the release of CCK from HNC was not affected by recombinant human Ifn-gamma at any dose tested (0.1, 1 and 10 nM). The increased release of CCK elicited by IL-1 was calcium-dependent, as was that induced by potassium (60 mM), but it was biphasic and had a different time course and a lower magnitude than those induced by potassium and veratridine. These results suggest that IL-1 activates pituitary-adrenal axis by stimulating CCK neurons in the hypothalamus and/or neurohypophysis to release CCK, since CCK has been implicated in the regulation of adrenocorticotropin release.

Stimulation by interleukin-1 (IL-1) of the release of rat corticotropin-releasing factor (CRF), which is independent of the cholinergic mechanism, from superfused rat hypothalamo-neurohypophysial complexes.

The effects of interleukin-1 (IL-1) and interferon-gamma (Ifn-gamma) on the release of corticotropin-releasing factor (CRF) from superfused hypothalamo-neurohypophysial complexes (HNC) of rats were examined in the present study. In this in vitro system, the release of CRF from HNC was not affected by any dose of human recombinant Ifn-gamma tested (0.1, 1 and 10 nM). In contrast, a rapid increase of CRF from HNC was elicited in a dose-dependent manner by human recombinant IL-1 alpha and -1 beta in concentrations of 0.1-10 nM. The involvement of the cholinergic system in the mediation of the stimulatory effect of IL-1 on CRF release was evaluated. Acetylcholine in concentrations of 1-100 nM also elicited a rapid increase of CRF. The increase in CRF release induced by 10 nM of acetylcholine was completely suppressed in the presence of both hexamethonium (10 microM) and atropine (50 microM), a nicotinic and a muscarinic receptor antagonist, respectively. On the other hand, the increase in CRF release induced by 10 nM IL-1 alpha or -1 beta was not affected by these two antagonists. These results indicate that IL-1 stimulates CRF release through an action on the hypothalamo-neurohypophysial system, most likely on the hypothalamus, and that the stimulatory effect of IL-1 is probably independent of the cholinergic system.

Prognostic value of electroencephalogram (EEG) in anoxic encephalopathy after cardiopulmonary resuscitation: relationship among anoxic period, EEG grading and outcome.

We studied the prognostic applicability of electroencephalograms (EEGs) of seventy-nine patients within 24 hours after successful cardiopulmonary resuscitation. The EEGs were classified into five grades according to a modified Hockaday's scale. The EEGs of grades I and II implied full recovery, while those of grade III gave a varied but generally unfavorable prognosis. Patients with grades IV and V EEGs survived in a vegetative condition or died without awakening. Eighteen patients showed EEG with periodic patterns, all of which led to a fatal or vegetative outcome. One case showed EEGs associated with periodic triphasic waves and repetitive sharp transients in the same record. Several cases showed EEGs with different periodic patterns in consecutive records. We conclude that an EEG is a good indicator of patient prognosis after cardiopulmonary resuscitation. However, the clinical significance of morphological differences of various periodic patterns that can occur during an EEG remains to be established.

[ACTH secretion in adrenocortical disorders].

Secretion of cortisol is under stimulatory regulation by ACTH, and cortisol secreted, in turn, inhibits ACTH secretion by the pituitary. Therefore, measurement of plasma ACTH is indispensable in the diagnosis of the adrenocortical diseases. The adrenal cortex is included in the hypothalamo-adenohypophysial-adrenocortical system, and the pathogenesis of these disorders must be evaluated. An interaction between the hypothalamo-adenohypophysial-adrenal system and the immune system have been suggested. We studied the effect of interleukin-1 (IL-1) on ACTH secretion by cultured rat pituitary cells in vitro. Our results suggest that IL-1 stimulates the ACTH secretion by enhancing its synthesis by the pituitary, rather than ACTH release.

[Radioreceptor assay of prolactin].

PIP: The authors prepared the prolactin marker with iodine-125 and made iodine-125-human prolactin and iodine-125-sheep prolactin. To make the complex, iodine-125-human prolactin was incubated with prolactin receptors isolated from female rat liver cell membranes. This complex is reversible and can be replaced by cold human prolactin. Studies with mammary glands of various animals have indicated that the prolactin receptor seemed to be a peptide or a protein of macromolecules in chemical nature. Estrogen enhanced the binding ability of iodine-125-sheep prolactin to prolactin receptor of rat liver cell membranes. The mammary cells from hyposectomized animals lost the binding ability, and this ability was not recovered even by estrogen administration. In experimental animals, the growth of mammary cancer, induced by dimethyl benzanthracene, was enhanced by the administration of prolactin and reduced by the introduction of an antiprolactin serum. Ergocornine which would suppress the secretion of prolactin also reduced the cancer growth. The factors which would increase the secretion of prolactin increased the tumor growth. Mammary cancer cells have generally less binding ability to prolactin than the normal mammary cells. These cancer cells in animals seem not to be prolactin dependent and have an autonomic nature. The relationship between prolactin and human mammary cancer is not yet entirely clear. However, there is a possibility that prolactin may play a role in certain mammary cancer. Reports on prolactin receptor in human mammary cancer cells are sparse. Although the authors found estrogen receptor in some mammary cancer cases, they were not able to find a significant amount of prolactin binding ability in these cells.^ieng

[A sensitive and specific radioimmunoassay for arginine vasopressin and its validation].

A sensitive and specific radioimmunoassay (RIA) for arginine vasopressin (AVP) has been developed and validated. Synthetic AVP was coupled to bovine serum albumin (BSA) with glutaraldehyde. Antisera against AVP were raised in three rabbits immunized with AVP-BSA complex. After 6 months, at the 16th injection, one of the antisera had a titer high enough to be utilizable for RIA at a final dilution of 1:400,000. The labeling of AVP with 125I Na was performed with the modified chloramine T method, and the purification of iodinated AVP was done with gel filtration chromatography on a Sephadex G-25 fine column (1 X 20 cm) with an elution buffer of 0.01 M acetic acid containing 0.1% BSA. Radioactivities from the Sephadex G-25 were eluted in three peaks. 125I-AVP, which was reactive to the antiserum, was contained in the third peak, and 125I-AVP in the fractions on the down slope of the peak was used for the radioligand in the amount of 1000 cpm. The specific activity of purified 125I-AVP was about 400 muCi/microgram. Diluted antiserum and samples, unlabeled AVP or related peptides were preincubated at 4 degrees C for 24 hr, and then 125I-AVP was added to the mixture and incubated for a further 72 hr. Separation of B and F was done with polyethyleneglycol. The minimal detection limit of AVP, which was 95% of the confidence limit of the mean value of B0, was 0.4 pg/tube. The cross-reactivities with lysine vasopressin, arginine vasotocin, DDAVP and oxytocin were 0.1%, 30%, 1% and 0%, respectively. AVP in plasma was extracted with cold acetone and petroleum ether. The recoveries of synthetic AVP from plasma which was added (2-16 pg) were more than 94%. The intra and inter-assay coefficients of variation determined by plasma of AVP concentration of about 4.8 pg/ml were 8.7% and 11.3%, respectively. The RIA detected AVP of concentration as low as 1 pg/ml following the extraction procedure. AVP immunoreactivity was detected without extraction in urine, and the lyophilized cerebrospinal fluid and acid extract of tissues of the central nervous system, and the reactivities in these samples were demonstrated to be immunologically identical to that of synthetic AVP when diluted serially. The changes of plasma and urinary AVP concentration on water intake, water deprivation and smoking in humans were clearly demonstrated.(ABSTRACT TRUNCATED AT 400 WORDS)

Plasma prolactin responses to thyrotropin-releasing hormone in patients with breast cancer.

Plasma human prolactin levels were measured by homologous radioimmunoassay in patients with primary breast cancer and in normal women of similar age. In normal controls mean (+/- SEM) basal plasma prolactin levels were 11.9 +/- 1.5 ng/ml and intravenous injection of synthetic thyrotropin-releasing hormone (TRH), 500 mug, caused a significant rise in plasma prolactin in all subjects examined with a maximum response of 52.6 +/- 3.3 ng/ml (mean +/- SEM). Markedly high plasma prolactin levels and exaggerated plasma prolactin responses to TRH were demonstrated in some patients with breast cancer. However, mean basal plasma prolactin levels and mean plasma prolactin increments following TRH in patients with breast cancer did not differ significantly from those in normal subjects. Plasma prolactin responses to TRH were slightly blunted during the administration of androgen in patients with breast cancer. These results suggest that some of the patients with primary breast cancer have abnormal prolactin secretion.