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Male and female rats were gonadectomized and subsequently (1-3 months later) treated with steroids (estradiol benzoate plus progesterone or testosterone propionate) preliminary to the intracarotid injection of either saline or a highly purified preparation of porcine LH-RH. Groups of animals were killed at 3, 5, 10 or 20 min after the injection. Serum and pituitary LH were measured by radioimmunoassay and serum FSH was examined by bioassay or radioimmunoassay. Representative pituitary glands from control groups and from groups responding strongly to LH-RH were studied by electron microscopy. The pituitary gonadotrophic cells were highly modified as a result of gonadectomy but no clear distinction into 2 types could be made. Ovariectomized, estrogen-progesterone (OEP) pretreated animals gave a greater response to the LH-RH injections than testosterone treated castrates of either sex or castrated male rats given ovarian steroids. At 5 min after the injection of 100 ng of LH-RH into OEP rats, serum levels of...

Non-stress levels of serum luteinizing hormone (LH), prolactin and corticosterone were determined at 3-hr intervals during controlled 24-hr light-dark cycles in adult male rats. Significant 24-hr periodicity was demonstrated for non-stress levels of serum LH, prolactin, and corticosterone; peak values for corticosterone, LH, and prolactin occurred at 5 PM, 8 PM and 11 PM respectively. In contrast, stress markedly reduced the amplitude in serum corticosterone and abolished the rhythm in serum LH concentrations; only serum prolactin showed significant periodicity following stress. These data suggest that circadian periodicity in serum levels of LH, prolactin, and corticosterone can be demonstrated for male rats provided adequate consideration is given to the effect of stress on adenohypophyseal function. (Endocrinology 90: 29, 1972)

Addition of nanogram amounts of highly purified or pure porcine LH-RH/FSH-RH, once daily for 5 days to female rat anterior pituitary cultures, significantly increased the release of both LH and FSH. LH release appeared to be linearly related to the log-dose of LH-RH/FSHRH over the range of S-40 ng/ml/day. Total content of LH and of FSH in stimulated tissue and medium exceeded that of controls as measured by radioimmunoassays for LH and FSH. Synthetic LH-RH/FSH-RH also stimulated the release and synthesis of both LH and FSH in rat anterior pituitary cultures. This indicates that both LH and FSH releasing activities are intrinsic to the same molecule. When anterior pituitary tissue was incubated with tritiated glucosamine in the presence of porcine LH-RH/FSH-RH, there was a significant incorporation of radioactivity into the LH found in the incubation medium. These data indicate that de novo synthesis, as well as release of LH, occurred in tissue stimulated with porcine LH-RH/FSH-RH. (Endocrinology 90: 764,...

Publisher Summary This chapter discusses the role of follicle-stimulating hormone (FSH)-releasing hormone and luteinizing hormone (LH)-releasing hormone. The involvement of the anterior pituitary in process of reproduction began with the discovery of gonadotropic activity in the pituitary. FSH stimulates the growth of the ovarian follicle by promoting mitotic proliferation of the granulosa cells. The response to FSH is demonstrable by the presence of follicles in all stages of development, initiation of antrum formation, and increase in ovarian weight. FSH is a gametogenic hormone in the male; it affects the function and structure of seminiferous tubules and production of spermatozoa. In the hypophysectomized rat and in hypophysectomized humans, FSH, given together with LH, stimulates spermatogenesis. The presence of androgens is necessary for full spermatogenesis. LH is responsible for stimulation of steroidogenesis in the ovarian follicle and for ovulation in the ovary previously stimulated by FSH and the transformation of the graafian follicles into corpora lutea. After ovulation, under the influence of LH, some granulosa cells increase in size and undergo the process of luteinization.

The nullification by actinomycin D (Act D) of the inhibitory effect of estrogen on the castration-induced rise in plasma luteinizing hormone (LH) level was studied in rats. Plasma LH levels were measured in ovariectomized rats injected with 3 mg testosterone or 50 μg estradiol benzoate and 25 mg progesterone 72 hr before sacrifice. It was found that ip administration (20 hr before sacrifice) of 100 Mg Act D/100 g bw caused a rise in plasma LH levels in ovariectomized rats treated with estrogen and progesterone, but not in those given testosterone. Act D did not increase plasma LH levels in normal rats or potentiate the effect of saline, plasma or LH in the ovarian ascorbic acid depletion (OAAD) assay. Act D did not block the response to LH-releasing factor (LRF), nor affect the uptake of 3H-estradiol, by the hypothalamus or the anterior pituitary. Act D (100 μg/100 g bw), given to estrogen and progesterone treated spayed female rats 20, 10 and 1 hr before sacrifice, nullified the estrogen and progesterone...

An attempt was made to evaluate the growth hormone (GH)-releasing activity in extracts of the stalk-median eminence region (SME) from kittens with bilateral lesions of the paraventricular nuclei, which showed a marked growth retardation, and from sham-operated animals. SME extract from the sham-operated control kittens induced a significant decrease in pituitary GH content. However, SME extract from kittens with bilateral lesions in the region of the paraventricular nuclei failed to induce the depletion of pituitary GH content. The cerebral cortical extracts from both groups elicited no effect on pituitary GH. These results show that the hypothalamus of the lesioned kittens has no GH-releasing activity, i. e. GH-releasing factor (GRF) is lacking. This suggests that, in kittens, the area of the paraventricular nuclei plays an important role in the synthesis of GRF, so that destruction of this area causes growth impairment.

SummaryPotent preparations of growth hormone-releasing factor (GRF) were prepared from bovine hypothalamic extracts, by the glacial acetic acid concentration procedure followed by gel filtration on Sephadex. Purified GRF is distinct from vasopressin, oxy-tocin, a-MSH and other hypothalamic-releasing factors.We are grateful to Dr. E. Muller for advice on the use of his GRF assay and to Dr. William Locke for help in preparation of the manuscript.

SummaryExperiments were performed in the rat to determine whether the increased secretion of growth hormone (GH) during stress involves augmentation of synthesis and/or release of hypothalamlc GH-releasing factor (GRF). Two different stimuli were used as stress: injection of formalin, which was previously shown to be ineffective in inducing GH release; and cold exposure, which evoked depletion of pituitary GH. Exposure of rats to cold (4°C) for 1 hr resulted in a significant depletion of pituitary GH, which was accompanied by disappearance of hypothalamic GRF and appearance of GRF activity in plasma. Cold exposure for 5 minutes was ineffective. Injection of 10% formalin did not induce pituitary GH depletion, or affect hypothalamic and plasma GRF activity. These results indicate that some stressful stimuli, such as cold exposure, capable of releasing GH, induce this effect via the hypothalamus; other stresses, like formalin injection, which do not release GH, exert little effect on the GH-release mechanism...

Syntheses by the conventional method are described of [Gln8]-LH-RH, [Leu8]-LH-RH and [Pro8] [Arg9]-LH-RH. These peptides were purified by column chromatography on CM-Sephadex and gelfiltration on Sephadex G-25 and proved to be homogeneous. The LH-RH and FSH-RH activities of these peptides were compared with those of natural LH-RH in vivo and in vitro . [Gln8]-LH-RH had significant LH- and FSH-RH activities, while [Leu8]-LH-RH and [Pro8] [Arg9]-LH-RH had lower activities.

Highly purified pig LH-releasing factor (LRF) was tested for the ability to inhibit pituitary prolactin secretion in vivo (PIF activity). Cervical stimulation induced a significant depletion of pituitary prolactin content in estrous rats. When extract equivalent to 1 fragment of pig stalk median eminence was given before the stimulation, the depletion of pituitary prolactin was completely blocked. On the other hand, pretreatment with 50 μg of purified LRF, equivalent to 300 fragments of pig SME, failed to block the prolactin depletion following cervical stimulation. Pork LRF used in these studies raised plasma LH in ovariectomized rats pretreated with estrogen and progesterone in as small a dose as 0.05 μg. One μg LRF also induced ovulation in Nembutal-blocked cyclic rats. Thus, highly purified pork LRF was clearly devoid of PIF activity. This supports our previous conclusion that LRF is different from PIF. (Endocrinology 80: 972, 1967)

Summary The complete amino acid sequence of porcine LH- and FSH- releasing hormone has been provisionally determined by the use on a micro-scale of the combined Edman-dansyl procedure coupled with the selective tritiation method for C-terminal analysis. These procedures were used directly on the digestion products of LH-RH with chymotrypsin and thermolysin, without separation of the fragments. Additional data were provided by high resolution mass spectral fragmentation of LH-RH. On the basis of these results, we propose the following decapeptide sequence for LH-RH: (pyro)Glu-His-Trp-Ser-Tyr-Gly-Leu-Arg-Pro-Gly-NH2.

Since our group has been scheduled to deliver the concluding presentation, we would like to mention topics not discussed by previous speakers. For this reason, our presentation had to be improvised in part during the preceding talks, so that it will be composed of many topics.

The interaction of corticotropinreleasing factor (CRF) preparations, dexamethasone and actinomycin D (Act D) on ACTH release from the rat pituitary was studied in vivo and in vitro. In in vivo studies, ACTH release, as indicated by plasma corticosterone levels, following iv injection of the crude rat pituitary stalk and median eminence (SME) extracts or a purified porcine hypothalamic CRF, was considerably suppressed by pretreatment of the rat with 400 μg/100 g body wt of dexamethasone ip. One hundred μg Act D/100 g body wt injected ip before, but not after, dexamethasone prevented the dexamethasone suppression of the action of these CRF preparations. In in vitro experiments, rat pituitaries released a considerable amount of ACTH into the incubation medium when 0.4–0.8 rat SME was added to the medium. When the pituitaries were preincubated with 2–20 μg/ml of dexamethasone for 2 hr, the amount of ACTH released by SME was greatly reduced. Preincubation with Act D, 0.5–2 μg/ml, also decreased SME-induced ACT...

SummaryEstrus activity was checked daily in three whitefaced, cross-bred, yearling ewes and jugular blood samples were collected daily during five estrous cycles. Serum prolactin and LH levels were determined by double radioimmunoassays. Prolactin levels were significantly higher during proestrus, (49 mμg/ml) and Day 1 estrus (40 mμg/ml) than during Day 2 estrus (11 mμg/ml), metestrus (15 mμg/ml) and diestrus (14 mμg/ml). LH levels were elevated on Day 1 estrus in only two of the five estrous cycles observed. The mean LH level for all five of the Day 1 estrus observations was 56 mμg/ml. This level was significantly higher than that during Day 2 estrus (1.9 mμg/ml), metestrus (1.6 mμg/ml), diestrus (1.1 mμg/ml) and proestrus (1.4 mμg/ml). These data suggest that the duration of the rise in prolactin levels is longer and precedes the elevated LH value at estrus. Serum prolactin levels did not seem to be correlated with the rise in LH, even though the increase in LH occurs at a time when serum prolactin leve...

In order to test if LH-RH also displays prolactin release-inhibiting activity, synthetic LH-RH was injected into intact diestrous rats and ovariectomized, estrogen-progesterone treated rats. Both groups of rats were pretreated with reserpine in order to increase serum prolactin levels. LH and prolactin were determined by radioimmunoassays. In spite of the fact that LH-RH brought about significant serum LH increase in both groups, no prolactin inhibition was seen. These results indicate that under the conditions of this investigation, LH-RH does not seem to display any prolactin release-inhibiting activity.

Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal polypeptide (VIP) immunoreactive cells were demonstrated in the hypothalamic magnocellular nuclei in cats and rats. In cats these immunoreactive cells were stained without any treatment or intervention; however, in rats we had to use the pituitary stalk section to enhance the amount of PACAP and VIP for successful immunostaining. In both species the regions occupied by PACAP and VIP immunoreactive cells partially overlap each other in the paraventricular and supraoptic nuclei. Nevertheless, in either cats or rats PACAP and VIP immunoreactivities do not colocalize in the same cells studied by double labeling immunohistochemistry (IHC) or by the combination of immunohistochemistry and in situ hybridization. As was expected, PACAP and VIP immunoreactive materials were stored in different fibers of the posterior pituitary where the distribution of PACAP and VIP fibers also showed different patterns: PACAP fibers form a dense plexus at the periphery of the posterior lobe, in the vicinity of the intermediate lobe; however, the VIP fibers were evenly distributed mainly in the center of the posterior lobe. In spite of the high sequence homology of PACAP and VIP, the two peptides are synthesized in different subpopulations of hypothalamic neurons. This different distribution correlates well with the different role of the hypothalamic PACAP and VIP in the biologic clock and in the functions of the anterior and posterior pituitary.

The effect of the administration of sheep anti-LHRH gamma-globulin (anti-LHRHG) on the maintenance of pregnancy was investigated in rats. Nidation was confirmed by laparotomy on day 7 or 8 of pregnancy. In one experiment, rats were then injected iv with 1 ml anti-LHRHG or normal sheep gamma-globulin (NSG) daily from days 7 to 11. The uteri were inspected again on day 14 of pregnancy, when it was found that complete resorption of the fetuses had occurred in the anti-LHRHG-treated rats, but that the fetuses were normal in the NSG-treated control rats. The effect of a single injection of 1 ml of anti-LHRHG on day 7, 8, 9, 10, 11, or 12 of pregnancy was also investigated. Administration on day 9 or 10 resulted in complete resorption of the fetuses by the time of the 2nd inspection on day 14, and treatment on day 8 or 11 was partially effective. However, treatment on day 7 or 12 exerted little effect on viability of the fetuses. None of the rats showed vaginal bleeding following treatment with anti-LHRHG. Termination of pregnancy by anti-LHRHG could be prevented by SC injection of 1 mug LHRH twice daily, or by 4 progesterone SC once daily, from days 9 through 12 of pregnancy. The ovaries of the rats treated with anti-LHRHG from days 7 to 11 were smaller than those of the NSG-treated control rats, and some of the corpora lutea underwent cystic degenerative changes. Lutein cells of the former were also smaller than those of the latter. Serum progesterone levels were reduced after a single injection of anti-LHRHG on day 9 or 10, but not on day 7 or 12 of pregnancy. There was excellent agreement between the reduction of serum progesterone and fetal resorption. Serum LH levels were low on days 7 through 12 in the anti-LHRHG-treated as well as the NSG-treated rats, and the possible suppressive effect of anti-LHRHG on LH could not be revealed because of insufficient sensitivity of the radioimmunoassay method. No significant difference was observed in serum prolactin levels between the groups of rats. The results clearly indicate that LHRH, by maintaining progesterone secretion, is indispensable on days 9 and 10 of pregnancy for the maintenance of pregnancy.

Immunoreactive somatostatin (IRS) was measured in whole hypophyseal portal blood of rats anesthetized with urethane, pentobarbital, or Althesin. The portal blood was collected directly into chilled 2 N acetic acid from the pituitary stalk stump after hypophysectomy. The acid-blood mixture was then extracted with acetone and washed with organic solvent. The mean (±SE) concentration and secretion rate of IRS in portal blood under urethane were 502.5 ± 52.9 pg/ml and 3.05 ± 0.42 pg/min, respectively, which were significantly higher than those under pentobarbital (113.1 ± 18.1 pg/ml and 1.09 ± 0.13 pg/min, respectively) or Althesin (155.4 ± 28.4 pg/ml and 1.43 ± 0.24 pg/min, respectively). The mean (±SE) IRS level in the jugular blood was 19.1 ± 4.7, 18.1 ± 6.7, and 15.5 ± 2.1 pg/ml under urethane, pentobarbital, and Althesin, respectively. Plasma GH levels were significantly lower in urethane and higher in pentobarbital- or Althesin-anesthetized rats than in decapitated rats. Somatostatin immunoreactivity of...

An effect of D-Trp6-LH-RH (superactive LH-RH agonist) in the pituitary and ovarian function was examined. Four regularly cycling baboons were used for this study. After determination of control values of plasma levels of LH, oestrogen and progesterone during the entire menstrual cycle, D-Trp6-LH-RH was infused subcutaneously for 7 days during the early luteal phase in these four baboons. An infusion of D-Trp6-LH-RH increased plasma LH and oestrogen, but it failed to alter the plasma level of progesterone. From these results, it seems unlikely that 1) D-Trp6-LH-RH has a luteolytic effect, and 2) an increased ovarian oestrogen causes luteolysis in the baboon.

Pituitary adenylate cyclase-activating polypeptide (PACAP) has recently been isolated from the frog brain and the sequence of the peptide appears to be strikingly similar to that of mammalian PACAP. In the present study, we have investigated the localization of PACAP in the frog interrenal (adrenal) gland by immunocytochemistry using antisera directed against PACAP 38 or PACAP 27. Two types of PACAP-immunoreactive fibres were observed: thick varicose fibres coursing between adrenal cells and thin processes located in the walls of blood vessels irrigating the gland. Bilateral transection of the splanchnic nerves did not affect the intensity and distribution of PACAP immunoreactivity. The mean ± s.e.m. concentration of PACAP, measured by radioimmunoassay in crude adrenal extracts, was 0·65 ± 0·16 nmol/g wet tissue. Two molecular forms of PACAP in the adrenal gland were characterized by reversed phase high-performance liquid chromatography combined with radioimmunoassay quantification. The elution profiles revealed the existence of two peaks exhibiting the same retention times as synthetic frog PACAP 38 (fPACAP 38) and PACAP 27, the predominant form being PACAP 38. The possible involvement of PACAP in the regulation of adrenal steroidogenesis was investigated in vitro using a perifusion system for frog adrenal slices. Graded doses of fPACAP 38 (0·1–10 μmol/l) increased the secretion of both corticosterone and aldosterone in a dose-dependent manner. Administration of repeated pulses of fPACAP 38 (1 μmol/l), at 120-min intervals, led to a reproducible stimulation of corticosteroid secretion without any tachyphylaxis. Prolonged infusion (2 h) of the peptide induced a rapid increase in corticosterone and aldosterone output, followed by a gradual decline in the secretion rate, suggesting the occurrence of a desensitization phenomenon. Synthetic porcine vasoactive intestinal peptide, which is structurally related to PACAP, was about ten times less potent than fPACAP 38 in stimulating steroidogenesis while the [Des-His1]-fPACAP 38 analogue was 100 times less effective. These results demonstrate that a peptide closely related to fPACAP 38 is present in fibres innervating the frog adrenal gland and could participate in the regulation of corticosteroid secretion, particularly during neurogenic stress. Journal of Endocrinology (1993) 139, 183–194

Pituitary adenylate cyclase-activating polypeptide (PACAP) is abundant not only in the brain, but also in the testis. Immunohistochemical studies have shown that PACAP-LI in rat testis is expressed stage specifically in spermatids. This suggests that testicular PACAP participates in the regulatory mechanism of spermatogenesis. Additionally, the ovary contains a relatively small amount of PACAP, conceivably involved in the regulation of folliculogenesis. PACAP is synthesized as a preprohormone and is processed by prohormone convertases, such as PC1, PC2, and PC4. PC4 is expressed only in the testis and ovary, where neither PC1 nor PC2 is expressed. However, whether PC4 is the sole endoprotease for the PACAP precursor in the gonads remains unknown. Recent studies using PC4-transgenic mice revealed that male PC4-null mice exhibited severely impaired fertility, although spermatogenesis appeared to be normal. The female PC4-null mice exhibited delayed folliculogenesis in the ovaries. To examine whether PC4 is the sole processing enzyme for the PACAP precursor in the gonads, we analyzed testicular and ovarian extracts from the PC4-null and wild-type mice for PACAP (PACAP38 and PACAP27) and its messenger RNA using reverse phase HPLC combined with specific RIAs and ribonuclease protection assay, respectively. For RIAs, three different polyclonal antisera with different recognition sites were used to identify PACAP38, PACAP27, and its precursor. Neither the testis nor the ovary from the PC4-null mice expressed PACAP38 or PACAP27, but the levels of PACAP transcripts in the testis and ovary of homozygous PC4-deficient mice were considerably elevated compared with those of the wild-type and heterozygous animals. The findings indicate that PC4 is the sole processing enzyme for the precursor of PACAP in the testis and ovary of mice. The possibility that the absence of bioactive PACAP in the testis and ovary of PC4-null mice caused severely impaired fertility in the males and delayed folliculogenesis in females warrants investigation.

The effect of the administration of sheep anti-LHRH gamma globulin (anti-LHRH-G) on implantation of fertilized ova was investigated in rats. Daily injections of 1 ml of anti-LHRH-G from Days 1 through 7 of pregnancy uniformly inhibited implantation of fertilized ova on Day 8, but viable sites, though considerably smaller in size than in control rats, became distinguishable on Day 14 in most rats. In some of these rats resorption of fetuses occurred, and others delivered pups 7-8 days after term. When the rats were given anti-LHRH-G from Days 3 through 5, the implantation was delayed by 5 days, but the gestation was not terminated. A single injection of 1 ml of anti-LHRH-G on Day 4 inhibited implantation on Day 8, but injection on Day 3 or 5 did not. The delayed implantation by anti-LHRH-G injected on Day 4 was nullified by concomitant administration of 2 sc injections of 1 mug of LHRH, or a single dose of 1 mug of estradiol. The data indicate that the hypothalamic LHRH is essentail on Day 4 of pregnancy for timely implantation of fertilized ova, probably by maintaining LH and, consequently, estrogen secretion.

An iv administration of 1 ml sheep antiserum to somatostatin (anti-SS) resulted in marked increases of both serum GH and TSH, with a peak 10--20 min after administration in male rats anesthetized with urethane or pentobarbital. Administration of anti-SS had no effect on serum PRL. Ablation of the basal medial hypothalamus abolished the rises of both serum GH and TSH after anti-SS administration. Intravenous injection of 1 ml rabbit antiserum to TRH (anti-TRH) decreased serum TSH levels 15 min after injection, whereas injection of normal rabbit serum did not affect TSH levels. Serum TSH levels did not rise after injection of anti-SS in rats pretreated with anti-TRH. On the other hand, pretreatment with anti-TRH did not affect the basal serum GH levels nor the anti-SS-induced GH release. The enhanced secretion of GH and TSH after anti-SS injections was not blocked by pretreatment with indomethacin, an inhibitor of prostaglandin synthesis. The following conclusions were made: 1) both GH and TSH responses to anti-SS require an intact basal medial hypothalamus; (2) TSH response to anti-SS is mediated by hypothalamic TRH; and 3) the GH response may be mediated by hypothalamic GH-releasing hormone which is not TRH or prostaglandins.

Interleukin 1 (IL-1) is a multifunctional cytokine produced by numerous cell types, including cells of the central nervous system (CNS). In the CNS, IL-1 produced by glia is thought to support trophic functions after brain injury. However, little is known about whether the IL-1 receptor (IL-1R) is expressed in brain cells and how these receptors might be regulated. Analysis of IL-1R expression in the human glioblastoma cell line U-87 MG indicated the presence of a specific, saturable, and high-affinity (dissociation constant = 104 +/- 14 pM) binding site, which was of moderately high density (1,228 +/- 156 sites/cell). Incubation of U-87 MG cells with cortisol or dexamethasone for as little as 6 h resulted in an upregulation of IL-1R expression, which could be blocked by coincubation with cycloheximide or actinomycin D. IL-1 beta downregulated the expression of its own binding site. Upregulation of the IL-1R by glucocorticoids (GCs) appeared to be coupled to the release of interleukin 6 (IL-6), since IL-1 was significantly more potent in inducing IL-6 release in U-87 cells that were preincubated in the presence of GCs compared with cells incubated in the absence of GCs. These results suggest that IL-1 acts on glial cells via a high-affinity receptor and indicate that GCs may amplify or prolong the actions of IL-1 in the CNS.

Synaptic contacts between growth hormone-releasing hormone (GHRH)- and somatostatin-containing neurons were demonstrated in the rat hypothalamus by a double-staining immunocytochemical method at the electron microscopic level. Somatostatin-immunoreactive nerve terminals synapse on GHRH-positive dendrites and cell bodies in the arcuate nucleus. A fine network of GHRH-immunopositive nerve terminals was observed at the light microscopic level in the rostral part of the periventricular nucleus and in the dorsal part of the arcuate nucleus around somatostatin-containing neuronal elements. With the electron microscopic synaptic contact between GHRH-containing nerve terminals and somatostatin-containing dendrites are demonstrated. The reciprocal innervation between GHRH- and somatostatin-containing neurons that project to the median eminence and regulate growth hormone secretion must allow them to coordiante their activities.

The luteinizing hormone-releasing hormone (LHRH) content of the medical basal hypothalamus was determined by radioimmunoassay 10 days after the isolation of this region. Between 70 and 90% of the LHRH disappeared from the hypothalamus after the surgical procedure. Thus, it seems that most of the LHRH present in the medial basal hypothalamus arises from, or is controlled by, cells elsewhere in the brain.

An antagonist of luteinizing hormone-releasing hormone (LH-RH). [D-Phe2-Phe3-D-Phe6]-LH-RH (Phe, phenylalanine), suppressed luteinizing hormone (LH) and follicle-stimulating hormone (FSH) release in male rats in response to LH-RH for at least 4 hours. Three subcutaneous injection of 1 milligram of this antagonist into rats during proestrus completely suppressed ovulation, while a single injection of 1.5 milligrams per rat inhibited 95.3 percent of the preovulatory surge of LH, 84.2 percent of the FSH surge, and suppressed ovulation by 86.4 percent.

A substance related to luteinizing hormone-releasing hormone was demonstrated, by immunohistochemical procedures, in the cytoplasm of interstitial cells within the rat testes. In many seminiferous tubules, nuclei of spermatogonial cells were also immunopositive. Both cytoplasmic and nuclear fractions of testicular homogenates contain immunoreactive compounds, and this report identifies which cell types contain this substance. The localization of a peptide hormone within the nucleus of a target cell population may indicate its mode of action.

ALTHOUGH publications concerning measurement of vasopressin and oxytocin in blood and urine are legion, the lack of specificity of technique for concentration and bioassay of the trace amounts presumed to be present in biological fluids has led to wide variation in results and frank scepticism concerning their physiological significance1. Since bioassay techniques, although extremely sensitive, are inherently subject to wide error, a reliable quantitative method applicable to biological fluids demands a specific and sensitive technique for isolation and concentration of these polypeptides from blood or urine prior to bioassay.

A synthetic decapeptide, corresponding to the chemical structure of luteinizing hormone-releasing hormone from porcine hypothalami, was tested for the induction of ovulation in golden hamsters that had previously been treated with phenobarbital to prevent spontaneous ovulation. Subcutaneous injection of 0.089 to 0.357 nanomole of this synthetic luteinizing hormone-releasing hormone stimulated release of luteinizing hormone and induced ovulation.

The effects of dimethylsulfoxide (DMSO) upon the topical absorption of vasopressin and adrenocorticotropin (corticotropin) in the rat and melanocyte stimulating hormone (MSH) in the frog were investigated. At a dose approximately 20,000 times that used intravenously, vasopressin absorption was slightly increased in one third of the rats by the application of DMSO, while corticotropin absorption was unaffected. The topical absorption of MSH in the frog was increased by DMSO in three of five experiments at a dose of MSH several hundred times that used in dorsal lymph sac injection. The small increase in topical absorption of these hormones seen in some animals after the application of DMSO, therefore, required extremely large doses.

WE have recently found that the decrease of ascorbic acid concentration of rats' adrenals due to epinephrine is smaller in rats to which pituitrin has been administered and in dehydrated rats than in normal rats1. This suggests that the posterior pituitary hormone depresses the adrenal cortical activity. The questions arise, whether the posterior pituitary hormone acts directly on the adrenal or indirectly through the depression of the anterior pituitary secretion, and which fraction of the posterior pituitary hormone, pressor or oxytocic, is responsible for this effect. The present work was undertaken to clarify these points.