Rat atrial natriuretic factor suppresses proopiomelanocortin-derived peptides secretion from both anterior and intermediate lobe cells and growth hormone release from anterior lobe cells of rat pituitary in vitro

Synthetic rat atrial natriuretic factor (ANF) was found to attenuate, in a dose-dependent manner, basal and corticotropin-releasing factor-induced secretion of proopiomelanocortin-derived peptides from cultured anterior and intermediate lobe cells of rat pituitary. ANF was also found to suppress basal and growth hormone-releasing factor-stimulated secretion of growth hormone from anterior lobe cells of rat pituitary. These results, together with reports of the existence of ANF-positive neurons in the hypothalamus and ANF-positive fibers in the median eminence, suggest that hypothalamic ANF is probably involved in the regulation of pituitary hormone secretion, especially that of proopiomelanocortin-derived peptides and growth hormone.

hpGRF-44-NH2, lot no. 92-81-5G-41-47, is (human) growth hormone-releasing factor containing no trace of (ovine) corticotropin-releasing factor

Recent analytical studies of aliquots of our preparation of hpGRF-44-NH2, lot no. 92-81-5G-41-47, as available here show it to be pure hGRF with no trace of oCRF. The mixture of 95% oCRF + 5% hGRF that Tannenbaum et al described under that code number, did not originate in our laboratory.

A divergence of plasma growth hormone response between growth hormone-releasing factor and insulin-induced hypoglycaemia among middle-aged healthy male subjects

The capability of the anterior pituitary gland to secrete GH in response to an intravenous injection of growth hormone-releasing factor (GRF) and insulin-induced hypoglycaemia was evaluated in 9 healthy male subjects ranging in age between 37 and 52 years old. Plasma GH response to 100 micrograms human GRF showed considerable intersubject variation and the increment of the peak value from the basal did not exceed 5 ng/ml in four out of 9 subjects. In contrast, insulin-induced hypoglycaemia resulted in a consistent stimulation of GH that exceeded 21 ng/ml in all subjects. The mean peak GH response after insulin-induced hypoglycaemia was significantly higher than that after GRF (27.4 +/- 1.6 vs 10.6 +/- 1.9 ng/ml). These results demonstrate that a significant divergence exists in plasma GH responses between the two provocative tests in the middle-aged subjects and suggest that the stimulation of GH following insulin-induced hypoglycaemia is not mediated solely by endogenous GRF.

Comparative effects of corticotropin-releasing factor, arginine vasopressin, and related neuropeptides on the secretion of ACTH and alpha-MSH by frog anterior pituitary cells and neurointermediate lobes in vitro

The ability of corticoliberin (CRF), urotensin I, sauvagine, arginine-vasopressin (AVP), and mesotocin to stimulate ACTH release by frog anterior pituitary cells and alpha-melanotropin (MSH) by frog neurointermediate lobe was studied in vitro using a perifusion technique. CRF and AVP were found to be potent stimulators of ACTH secretion, whereas urotensin I and sauvagine were totally inactive. In opposition to recent findings in the rat. CRF did not modify alpha-MSH secretion by the frog neurointermediate lobe. Mesotocin, which is present in the parenchymal cells of the frog pars intermedia, had no effect on alpha-MSH release in vitro. No potentiation of CRF-induced ACTH release was observed when anterior pituitary cells were incubated with a combination of AVP and CRF. Together with the recent elucidation of a CRF-like molecule in the frog diencephalon, these results suggest that, in Amphibia, CRF and AVP exert their stimulatory action specifically on distal lobe corticotrophs.

The responses of plasma adrenocorticotropin and cortisol to corticotropin-releasing hormone (CRH) and cerebrospinal fluid immunoreactive CRH in anorexia nervosa patients

Pituitary-adrenocortical responses to the iv injection of 100 micrograms synthetic ovine corticotropin-releasing hormone (CRH) were studied in 13 patients with anorexia nervosa, and the concentrations of immunoreactive CRH in cerebrospinal fluid were measured in 7 of them. Mean basal levels of plasma ACTH and cortisol were 32 +/- 5 pg/ml (+/- SEM) and 21.1 +/- 1.5 micrograms/dl, respectively. The latter value was significantly higher than that in age-matched normal women (P less than 0.005). The mean increments of plasma ACTH and cortisol in response to CRH injection in those 13 patients were 21 +/- 5 pg/ml and 5.3 +/- 1.7 micrograms/dl, respectively, significantly lower than those in normal women (58 +/- 6 pg/ml and 15.3 +/- 7.7 micrograms/dl, respectively; P less than 0.005). When 4 patients were reexamined after weight gains of between 3 and 22 kg, their responses to the CRH injection increased. The mean concentration of immunoreactive CRH in the cerebrospinal fluid of seven patients was 30.8 +/- 3.9 pg/ml (+/- SEM), which was higher than the value of 18.4 +/- 1.1 pg/ml (P less than 0.005) in control subjects with cervical spondylosis. These findings suggest the possibility that hypersecretion of CRH may occur in patients with anorexia nervosa.

In vitro study of frog (Rana ridibunda Pallas) interrenal function by use of a simplified perifusion system. VIII. Structure-activity relationship of synthetic ACTH fragments and gamma-MSH

The present study was undertaken to determine the structure-activity relationships of ACTH analogs on corticosteroid production by frog adrenal gland. Rana ridibunda interrenal dice were perifused with amphibian culture medium for 10 hr. Corticosterone and aldosterone concentrations were measured in the effluent perifusate using sensitive and specific radioimmunoassay methods. Perifusion of interrenal fragments with increasing concentrations of synthetic human ACTH 1-39 (ranging from 6.25 X 10(-11) to 10(-9) M) led to a linear log-dose increase in both corticosterone and aldosterone secretion. Thus, this model made it possible to compare the steroidogenic potency of several ACTH analogs. Synthetic alpha-MSH and its des-N alpha-acetyl derivative were found to be approximately equipotent, and 5 X 10(3) times less active than authentic ACTH. The short-chain analog ACTH 1-10 was 2 X 10(4) times less potent than ACTH whereas ACTH 4-10 was totally inactive. A fragment of the N-terminal region of the proopiomelanocortin molecule, gamma 3-MSH, caused a dose-related stimulation of steroid secretion. However, in contrast to what has been observed in the rat, gamma 3-MSH did not potentiate the corticotropic action of ACTH on frog interrenal gland. Since processing of proopiomelanocortin in frog intermediate lobe generates high amounts of alpha-MSH and des-N alpha-acetyl alpha-MSH, these results suggest that in amphibians, several peptides other than ACTH may be involved in the control of corticosteroidogenesis.

Thyroid-stimulating autoantibodies usually contain only lambda-light chains: evidence for the "forbidden clone" theory

Burnet's "forbidden clone" theory would predict that in patients with Graves' disease the pathogenic thyroid-stimulating autoantibody (TSab)-secreting clones arise by somatic mutation. Because each lymphocyte and its progeny are permanently committed to producing antibodies of a single light chain type, a clone arising by somatic mutation occurring in a single cell would be expected to produce autoantibodies of exclusively kappa or exclusively lambda type in an individual patient. Using affinity chromatographic techniques and monoclonal antibodies, we investigated the light chain type of TSab in 11 patients with Graves' disease. In all patients tested, TSab activity was confined to a single light chain type, confirming the recent work of Zakarija who used affinity chromatography with polyclonal antisera, but contrasting with earlier studies which used immuno-precipitation methods. Furthermore, the light chain type was lambda in 10 of the 11 patients. These observations provide support for the forbidden clone theory. In addition, the marked preponderance of patients producing TSab of the lambda-light chain type indicates that TSab are more likely to arise from the lambda repertoire of clones than from the kappa repertoire and suggests that immunoglobulin light chain V genes may be genetic determinants for susceptibility to Graves' disease.

Relative potencies of human, rat, bovine/caprine, porcine and ovine hypothalamic growth hormone-releasing factors to release growth hormone by the rat anterior pituitary in vitro

Synthetic rat, human, bovine/caprine, porcine and ovine growth hormone-releasing factor (GRF) were tested for their capacity to release growth hormone (GH) by the rat anterior pituitary in vitro. All peptides elicited parallel and dose-dependent increases in GH release and produced similar maximal GH secretion. Rat GRF was 3-6 times more potent in stimulating the release of GH than all other GRFs, while human, bovine/caprine, porcine and ovine GRF had potencies that were not statistically different. The increased potency of both rat GRF(1-27)NH2 and rat GRF(1-23)NH2 when compared to human GRF(1-27)NH2 and human GRF(1-23)NH2, respectively, suggests that the increased potency of this molecule resides in structural differences in the amino terminal of native GRF. The results demonstrate increased sensitivity of rat pituitary cells for their homologous releasing factor.

Rheumatic diseases in an Inuit population

Prevalence and incidence rates for rheumatic diseases were found to be minimal among the Inuit people in the Keewatin District of the Northwest Territories, Canada. Patient identification was achieved by a review of medical records. All identified patients were interviewed and examined by a participating rheumatologist. Among women, the prevalence of rheumatoid arthritis, adjusted for age of the Manitoba population, was 1,822 per 100,000 and was comparable with that observed in other populations; no cases of rheumatoid arthritis in men were confirmed. The age-adjusted prevalence of osteoarthritis, 1,219 per 100,000 in men and 2,144 per 100,000 in women, was apparently low. A moderately high incidence of Reiter's syndrome, 24.9 per 100,000, was found. The findings in children suggested a high frequency of seronegative spondylarthropathies (yearly incidence 60.1 per 100,000), although the adjusted yearly incidence for juvenile rheumatoid arthritis also appeared to be high, 23.6 per 100,000. The frequencies of HLA antigens in patient groups were compared with those found in 19 patients with musculoskeletal complaints but no rheumatic disease. Both HLA-B27 and HLA-DR4 appeared to be common in these controls, 36.8% and 63.2%, respectively. Nevertheless, there was a higher frequency of HLA-B27 in patients with seronegative spondylarthropathies (87%) than in controls (P = 0.001). Because of the small numbers of patients who had rheumatoid arthritis, no associations with HLA were made for this condition. Although the findings suggest differences in the distribution of rheumatic diseases compared with those found in other populations, more complete studies are required to confirm these observations.

Growth hormone-releasing factor: a new chapter in neuroendocrinology

The isolation and characterization of growth hormone-releasing factor (GRF) has initiated a new and exciting era in our understanding of the neuroendocrine regulation of pituitary growth hormone (GH) secretion. This report briefly describes the isolation and characterization of GRF, factors which modulate the GH response to GRF and the effects of chronic administration and deprivation of GRF on somatic growth. The intent of this report is to serve as a general introduction on biochemical and physiological aspects of GRF. The following reports from this symposium will then cover many of these topics in much greater detail.

Immunohistochemical evidence that growth hormone-releasing factor (GRF) neurons contain an amidated peptide derived from cleavage of the carboxyl-terminal end of the GRF precursor

Antisera were raised against synthetic replicates of the carboxyl-terminal (C-terminal) fragment of the precursor to human GH-releasing factor (GRF) (pre-proGRF) whose structure was predicted from the complementary DNA cloned from a pancreatic tumor. These antisera were used along with antisera to human GRF itself to search for the presence of related molecules in the human hypothalamus, with an immunohistochemical approach. The antisera to pre-proGRF that recognize specifically the C-terminal amidated form of pre-proGRF stain GRF neurons in their cell bodies, fibers, and nerve endings that are in contact with portal capillaries of the median eminence. Antisera against the nonamidated form of the molecule did not give any staining in the hypothalamus. These results strongly suggest that human hypothalamic GRF derives from a precursor immunologically related (and probably identical) to the tumorous one and that this precursor is cleaved inside GRF cell bodies to give, in addition to the GRF-44-NH2 a second amidated peptide, the C-terminal pre-proGRF that is transported distally to nerve endings and most probably coreleased with GRF into portal capillaries.

Cross-sectional seroepidemiologic study of the prevalence of cytomegalovirus and herpes simplex virus infection in a Canadian Inuit (Eskimo) community

The prevalence of antibody to cytomegalovirus (CMV) and herpes simplex virus (HSV) was determined, using enzyme-linked immunosorbent assay techniques, in a cross-sectional serologic survey of an isolated northern Canadian Inuit (Eskimo) community. The population studied included 155 Inuit and 11 Caucasian residents. By 6 years of age, 80% of the Inuit population were seropositive for CMV and 100% for herpes simplex virus. While only 7/63 Inuit greater than 20 years were seronegative for CMV, 5/11 Caucasian residents were seronegative (p = 0.01). For the Inuit population, no association between seropositivity for CMV and seropositivity for hepatitis A or hepatitis B was observed. This prevalence survey shows a serologic profile for infection with CMV and HSV in this northern Inuit community with an early age of acquisition and high prevalence of infection characteristic of socioeconomically deprived populations throughout the world, and is distinct from that observed in many other North American populations.

Subclass distribution of IgG autoantibodies in bullous pemphigoid

The distribution of IgG subclasses in the antibasement membrane zone autoantibody of pemphigoid in skin and serum was analyzed by use of monoclonal antibodies to human IgG subclasses. The predominant subclass was IgG4 which was present in 23 of 24 skin biopsies, IgG1 was next and IgG3 was found only occasionally. In 3 of 24 biopsies IgG4 was the only IgG subclass detected, C3 was absent in 2 of these, the third contained IgM and C3. Serum autoantibodies were similarly analyzed by indirect immunofluorescence (IIF) when again IgG4 autoantibody was the dominant subclass. No IgE autoantibody was detected by IIF.

Complementary DNA sequences of ovarian follicular fluid inhibin show precursor structure and homology with transforming growth factor-beta

Inhibin, a specific and potent polypeptide inhibitor of the secretion of follicle-stimulating hormone (FSH), of gonadal origin and thus a potential contraceptive, may constitute a missing link in the mechanism controlling the differential secretion of the pituitary gonadotropins. Inhibin-like bioactivity has been reported in various fluids and extracts of testis and in ovarian follicular fluid. Although there have been several attempts to purify inhibin from seminal plasma, purification from follicular fluid has been more successful (refs 14-16; for review see ref. 17). We have previously isolated two forms (A and B) of inhibin from porcine follicular fluid. Each form comprised two dissimilar subunits of relative molecular mass (Mr) 18,000 (18K, referred to here as the alpha-subunit) and 14K (the beta-subunit), crosslinked by one or more disulphide bridge(s). Forms A and B differ in the N-terminal sequence of their 14K subunit. Preliminary structural characterization of porcine and bovine ovarian inhibins shows that they have similar properties. Here, we have used the N-terminal amino-acid sequence data on the subunits of each inhibin to identify cloned complementary DNAs encoding the biosynthetic precursors and report that inhibins are the product of a gene family that also includes transforming growth factor-beta (TGF-beta) and whose structural organization is similar to that of pituitary and placental glycoprotein hormones.

Secretion of N-terminal pro-opiomelanocortin-derived peptides in response to acute haemorrhagic stress in conscious sheep

To determine whether peptides derived from the N-terminus of the corticotropin/melanotropin/endorphin precursor, pro-opiomelanocortin, are released into blood in response to acute haemorrhagic stress, we examined the effect of haemorrhage on plasma concentrations of immunoreactive gamma 3-melanotropin, beta-endorphin and cortisol. Plasma concentrations of immunoreactive gamma 3-melanotropin (mean +/- SEM) increased within 30 min of haemorrhage from 71.1 +/- 10.4 to 106.8 +/- 6.3 fmol/mL (p less than 0.01) and plasma cortisol increased from 16.2 +/- 3.8 to 85.9 +/- 22.4 pmol/mL (p less than 0.025). The changes in plasma immunoreactive gamma 3-melanotropin and beta-endorphin were positively correlated (p less than 0.025). This study shows that peptides derived from the N-terminus of pro-opiomelanocortin are co-secreted with the C-terminal peptide beta-endorphin during acute haemorrhagic stress in sheep.

Primary structure of bovine brain acidic fibroblast growth factor (FGF)

The major anionic mitogenic polypeptide for endothelial cells, acidic fibroblast growth factor (FGF), has been purified to homogeneity from bovine brain and its complete primary structure established by gas-phase sequence analysis. The 140 amino acid (Mr 16,000) protein has been previously shown to be a potent growth factor for many diverse cell types of mesodermal origin, in vitro, and an angiogenic agent, in vivo. The amino acid sequence of bovine brain acidic FGF has a 53% absolute homology with that of bovine pituitary basic FGF suggesting that these endothelial cell mitogens are derived from a single ancestral gene.

Isolation and partial characterization of an endothelial cell growth factor from the bovine kidney: homology with basic fibroblast growth factor

Two kidney-derived mitogens have been isolated by ion exchange, heparin-Sepharose and reverse-phase high-performance liquid chromatography on the basis of their capacity to stimulate the proliferation of bovine vascular endothelial cells in vitro. Gas phase sequence analysis identified the amino terminal sequences His-Phe-Lys-Asp-Pro-Lys-Arg-Leu-Tyr-X-Lys-Asn-Gly-Gly-Phe-Phe-Leu and His-Phe-Lys-Asp-Pro-Lys-Arg-Leu, respectively. The sequences are identical to residues 16-32 and 16-23 of bovine basic pituitary Fibroblast Growth Factor (FGF). The possibility that these kidney-derived mitogens are related, if not identical, to pituitary basic FGF is supported by the observations that they have similar molecular weights (15-16 kDa), similar retention behavior on all steps of chromatography and similar amino acid compositions, and they share at least some structural homology. Moreover, the kidney-derived growth factors, like basic FGF, are potent stimulators of capillary endothelial cells, granulosa cells, adrenocortical cells and vascular smooth-muscle cells (ED50 = 50 pg). The results demonstrate the existence of a kidney-derived FGF and suggest that at least some of the mitogenic, angiogenic and neovascularising activities described to be present in the kidney are due to the presence of an FGF-like molecule in this tissue.

Isolation and partial characterization of a Mr 32,000 protein with inhibin activity from porcine follicular fluid

A Mr 32,000 protein with inhibin activity was isolated from porcine follicular fluid by heparin-Sepharose affinity chromatography, gel filtration on Sephacryl S-200, and four reversed-phase HPLC steps. The isolated molecule is composed of two chains having molecular weights of 18,000 and 14,000, respectively, and bound together by disulfide bonds. Amino acid sequence analysis revealed the 10 NH2-terminal residues of the Mr 18,000 chain to be Ser-Thr-Ala-Pro-Leu-Pro-Trp-Pro-Trp-Ser- and those of the Mr 14,000 chain to be Gly-Leu-Glu-Xaa-Asp-Gly-Arg-Thr-Asn-Leu-. This Mr 32,000 protein specifically inhibits the basal secretion of FSH, but not that of LH, in the rat anterior pituitary monolayer culture system, with a half-maximal effective dose of 450 pg/ml.

Effect of hypothalamic ventromedial lesions on plasma growth hormone response to growth hormone-releasing factor in rats

The effect of ventromedial-arcuate (VMH-ARC) nuclei lesions on plasma growth hormone (GH) response to human growth hormone-releasing factor (GRF, 1 microgram/kg b.wt., i.v.) was studied in conscious rats after they had received chlorpromazine (CPZ) or CPZ plus antiserum against somatostatin (ASS). When rats were pretreated with CPZ alone, there was no difference in basal plasma GH level between VMH-ARC lesioned rats and controls. The magnitude of plasma GH response to GRF in 5 out of 6 VMH-ARC lesioned rats exceeded that of controls. When the same observation was repeated using the same rats after they had received ASS and CPZ, basal plasma GH levels of controls were significantly higher than those of VMH-ARC lesioned rats, and the magnitude of the plasma GH response to GRF was augmented in both groups of rats. The plasma GH response to GRF was comparable between two groups, though the peak plasma GH response to GRF was slightly but significantly lower in VMH-ARC lesioned rats as compared to controls. Pituitary GH content was reduced significantly in VMH-ARC lesioned rats as compared to controls. The results demonstrate that the pituitary responsiveness to GRF does not appear to be altered significantly in rats bearing bilateral VMH-ARC lesions. In addition, the placement of electrolytic lesions in VMH-ARC regions causes reduced SS secretion into the hypophyseal portal vessels and leads to an augmentation of plasma GH response to GRF.

Plasma growth hormone response to human growth hormone releasing factor in rats administered with chlorpromazine and antiserum against somatostatin. Effects of hypo- and hyperthyroidism

The effect of hypo- and hyperthyroidism on the plasma growth hormone (GH) response to synthetic human growth hormone releasing factor (GRF) was determined in conscious, freely moving rats pretreated with chlorpromazine and antiserum against somatostatin. Chlorpromazine plus somatostatin antiserum pretreated rats gave consistent response to GRF which was not observed in untreated rats. Chlorpromazine alone has no effect on GH secretion induced by GRF in rat pituitary monolayer culture. In rats made hypothyroid by thyroidectomy, both basal and peak plasma GH responses to a small (0.25 microgram/kg bw) and a moderate dose of GRF (1 microgram/kg bw) were significantly reduced as compared to controls. In rats made hyperthyroid by the administration of thyroxine, basal and peak plasma GH responses to a small but not to a moderate dose of GRF were significantly reduced as compared to controls. A reduced plasma GH response to a small dose of GRF was observed 8 days after the cessation of thyroxine administration. The pituitary GH reserve was markedly reduced in hypothyroid but not in hyperthyroid rats as compared to their respective controls. These results indicate that plasma GH response to GRF is reduced both in hypo- and hyperthyroidism. The mechanism involved in the phenomenon appears to be different between the two conditions.

Primary structure of bovine pituitary basic fibroblast growth factor (FGF) and comparison with the amino-terminal sequence of bovine brain acidic FGF

The two major mitogenic polypeptides for endothelial cells have been purified to homogeneity. The complete primary structure of bovine pituitary basic fibroblast growth factor (FGF) and the amino-terminal amino acid sequence of bovine brain acidic FGF have been established by gas-phase sequence analyses. Homogeneous preparations of these polypeptides are potent mitogens (basic FGF, ED50 approximately equal to 60 pg/ml; acidic FGF ED50 approximately equal to 6000 pg/ml) for many diverse cell types including capillary endothelial cells, vascular smooth muscle cells, and adrenocortical and granulosa cells; in vivo, basic FGF is a powerful angiogenic agent in the chick chorioallantoic membrane assay. The available protein sequence data demonstrate the existence of significant structural homology between the two polypeptides.

The inter- and intra-subject variabilities of plasma GH response to human growth hormone-releasing hormone (1-44) NH2 in men

The effects of intravenously given human growth hormone-releasing hormone (1-44) NH2 (hGRH-44) on growth hormone (GH) secretion were studied in normal men. A wide variability of intersubject GH response to hGRH-44 was observed. The peak plasma GH levels in response to 50, 100 and 200 micrograms hGRH-44 in 7 normal men were 9.1 +/- 3.2 ng/ml (Mean + SEM), 19.3 +/- 3.3 ng/ml and 22.4 +/- 4.0 ng/ml, respectively. Both the mean peak values for plasma GH response to 100 and 200 micrograms were significantly greater than that for 50 micrograms hGRH-44 injection (p less than 0.01), although there was no significant difference of the mean peak plasma GH values and mean concentrations at each time point, except for those at 120 min, when 100 or 200 micrograms hGRH-44 was administered. A significant difference in the mean amount of plasma GH secreted in response to hGRH-44 was observed only between 50 and 200 micrograms hGRH-44 injection (p less than 0.01). Furthermore, a dose-related plasma GH increase in response to hGRH-44 was not always observed in each subject. In contrast to the wide intersubject variability, the difference among responses of plasma GH to 100 micrograms or 200 micrograms of hGRH-44 given at multiple times separated by intervals of at least 1 week in each individual was relatively small.(ABSTRACT TRUNCATED AT 400 WORDS)

Immunoreactive and biologically active growth hormone-releasing factor in the rat placenta

Rat placentas from fetuses of 18 and 20 days of gestation were collected, extracted, and examined for their capacity to stimulate GH release in vitro. The crude extract stimulated, in a dose-dependent fashion, GH release by rat anterior pituitary cells in monolayer culture. The biological and immunological activities retained on antirat GH-releasing factor immunoaffinity columns eluted on Sephadex G-75 (fine) columns with an estimated mol wt of 5000 daltons. Reverse phase HPLC of this material revealed the presence of two forms of GRF activity that eluted with retention times identical to those of synthetic rat GRF and its methionine sulfoxide counterpart [Met(O)27]GRF. The results demonstrate the presence of an immunoreactive and biologically active GRF in the rat placenta that is indistinguishable from rat hypothalamic GRF.

The satiety effect of growth hormone-releasing factor in rats

The effect of growth hormone-releasing factor (GRF) on feeding behavior in rats was examined. Starvation-induced feeding was suppressed by intraventricular administration of 1 nmol and 4 nmol of synthetic human GRF (hGRF). Food intake was not affected when the peptide was administered by intraperitoneal injection. Furthermore, centrally administered hGRF also suppressed feeding in hypophysectomized rats. These results suggest that GRF suppression of food intake is mediated through the central nervous system independent of its effect on pituitary growth hormone secretion.