Low cerebrospinal fluid concentrations of peptide histidine valine and somatostatin-28 in Alzheimer's disease: altered processing of prepro-vasoactive intestinal peptide and prepro-somatostatin.

Recent studies have indicated that deposition of beta amyloid peptide in the brains of patients with senile dementia of the Alzheimer type (SDAT) is a consequence of abnormal processing of the beta amyloid protein precursor. In addition, reduced concentrations of various peptides have been measured in post-mortem brain tissue and cerebrospinal fluid (CSF) of patients with SDAT. We determined concentrations of the peptides derived from prepro-vasoactive intestinal peptide (VIP)--peptide histidine methionine-27 (PHM-27), peptide histidine valine (PHV) and VIP--and peptides derived from prepro-somatostatin (prepro-SS), SS-14 and SS-28, in CSF of patients with SDAT by radioimmunoassay combined with high performance liquid chromatography. We found significantly reduced levels of total PHM-immunoreactivity (IR) and PHV, and unaltered levels of PHM-27 and VIP in SDAT, compared with those in controls. Total SS-IR and SS-28 concentrations were significantly reduced in SDAT, while SS-14 levels did not differ from those of controls. These results suggest that an altered processing of the prepro-peptides of VIP and SS may occur in SDAT and that these alterations might have a significant role in the pathogenesis of SDAT.

Peptide histidine methionine and vasoactive intestinal peptide levels in human cerebrospinal fluid: age-related changes and absence of a correlation with serum prolactin.

Serum levels of prolactin (PRL), peptide histidine methionine (PHM) and vasoactive intestinal peptide (VIP) were measured in 97 subjects and cerebrospinal fluid (CSF) levels of PHM and VIP were measured in 50 subjects by specific radioimmunoassays to investigate correlations between them. The chromatographic studies revealed that PHM and C-terminal extended form of PHM, peptide histidine valine occurred in human serum and CSF. Significant age-related increases of CSF PHM (P < 0.02) were observed in both males and females, whereas an age-related decrease of serum PRL level was found in females (P < 0.01). In contrast, neither serum VIP, serum PHM nor CSF VIP changed significantly with age. There was a significant positive correlation (P < 0.002) between VIP and PHM in serum, but not in CSF. The close relation between VIP and PHM in serum meets one's expectation because of their derivation from a common precursor. In CSF, these two peptides did not change in parallel with each other. These results may reflect the alteration in metabolism of PHM in CSF. Finally, there was no correlation between serum PRL concentrations and either serum or CSF levels of the peptides, suggesting that neither VIP nor PHM levels in CSF as well as in serum can influence the basal PRL secretion in subjects without endocrine disorders.

Peptide histidine methionine in cerebrospinal fluid of patients with senile dementia of the Alzheimer type.

Immunoreactivities (IRs) of peptide histidine methionine (PHM) as well as somatostatin and vasoactive intestinal peptide (VIP) in the cerebrospinal fluid (CSF) were measured in patients with senile dementia of the Alzheimer type (SDAT) and age-matched control subjects. We found statistically significant reductions in the PHM-IR and somatostatin-IR levels in the CSF from patients with SDAT, as compared with those of the controls. However, the VIP-IR level in the CSF from SDAT was not different from that of the controls. These results suggest that selective degeneration of neurons containing somatostatin and PHM or the alteration in metabolism of PHM in the CSF might occur in SDAT.

Alpha 2-adrenergic control of growth hormone (GH) secretion in conscious male rabbits: involvement of endogenous GH-releasing factor and somatostatin.

In an attempt to clarify the regulatory role in GH secretion of central alpha-adrenergic and dopaminergic mechanisms, the effects of iv administration of alpha 1- and alpha 2-adrenergic antagonists and dopaminergic antagonists were investigated in undisturbed conscious male rabbits. During a 6-h observation period (1030-1630 h), control animals demonstrated spontaneous pulsatile GH secretion with mean (+/- SEM) 6-h GH levels of 6.49 +/- 0.54 ng/ml (n = 16). Intravenous injection of yohimbine (YOM; an alpha 2-antagonist), chlorpromazine (CPZ), and haloperidol (HAL; dopamine and alpha-adrenergic antagonists) completely suppressed this pulsatile GH secretion (mean 6-h GH levels, 2.98 +/- 0.24, 3.48 +/- 0.24, and 2.91 +/- 0.29 ng/ml, respectively; P less than 0.001), whereas prazosin (an alpha 1-antagonist), pimozide (a selective dopamine antagonist), sulpiride, and YM-09151-2 (YM; D2-specific antagonists) failed to affect the GH secretory pattern (mean 6-h GH levels, 6.61 +/- 0.73, 6.71 +/- 0.56, 5.44 +/- 0.44, and 6.87 +/- 1.44 ng/ml, respectively). While an iv injection of 2 micrograms synthetic human GH-releasing factor-(1-44)-NH2 (hGRF) induced GH rises in prazosin-, HAL-, pimozide-, sulpiride-, and YM-treated rabbits as well as control rabbits, YOM and CPZ completely abolished these GH responses to hGRF injection. An iv injection of 10 ml antisomatostatin gamma-globulin caused a prompt and transient GH rise, followed by a sustained elevation of GH trough levels in normal control rabbits. YOM treatment completely abolished this highly oscillated GH release. However, suppression by YOM or CPZ of hGRF-induced GH rises was significantly reversed by iv administration of 10 ml antisomatostatin gamma-globulin. Therefore, the inhibitory effect of YOM and CPZ on both episodic GH release and hGRF-induced GH rises is due to the enhanced release of somatostatin, with a simultaneous suppression of endogenous GRF. On the other hand, HAL, possessing a weaker alpha-blocking action than CPZ, blunted pulsatile GH secretion, but only modestly suppressed hGRF-induced GH rises. These results suggest the following. 1) Central alpha 2-adrenergic mechanisms play a more important role in the regulation of GH secretion than alpha 1-adrenergic mechanisms in the rabbit as well as in other species. 2) The alpha 2-adrenergic blockade causes suppression of the release of hypothalamic GRF and enhanced release of endogenous somatostatin, thereby suppressing GH secretion.(ABSTRACT TRUNCATED AT 400 WORDS)

Thyroid hormone regulates vasoactive intestinal peptide (VIP) mRNA levels in the rat anterior pituitary gland.

Vasoactive intestinal peptide (VIP) is a secretagogue for pituitary prolactin, but the importance of this peptide in the normal control of prolactin secretion is unclear. Recent studies suggest VIP synthesis within the rat anterior pituitary. We have shown (Endocrinology 124:1077) that the content of rat pituitary VIP increases in hypothyroidism. To confirm in situ pituitary synthesis of VIP and determine whether thyroid hormone effects on pituitary VIP relate to changes in VIP mRNA, Northern and in situ hybridization analyses of VIP mRNA in rat pituitaries were performed. Northern hybridization demonstrated an RNA species from rat pituitary consistent with rat VIP mRNA. Hypothyroidism increased the content of pituitary VIP mRNA, and replacement with 1-thyroxine prevented this increase. In situ hybridization showed multiple, widely-distributed hybridizing cells in pituitaries from hypothyroid animals. A distinct population of VIP-producing pituitary cells exists which may serve to modulate prolactin secretion in a paracrine or autocrine fashion.

Vasoactive intestinal peptide in the anterior pituitary is increased in hypothyroidism.

Vasoactive intestinal peptide (VIP) and PRL have been reported to be colocalized in rat lactotropes. To determine whether induced hypothyroidism, known to reduce pituitary PRL concentration, also reduces pituitary concentration of VIP, rats were treated with antithyroid drugs for 3 weeks. Pituitary PRL concentration in male rats (micrograms/mg protein) was markedly reduced by this treatment (9.4 +/- 1.0 vs. 2.3 +/- 0.4 when extracted at pH 1.1, 17.9 +/- 3.0 vs. 3.4 + 0.4 when extracted at pH 7.4, 21.8 +/- 3.3 vs. 6.7 + 1.3 when extracted at pH 10.0). Contrary to expectation, pituitary VIP concentration was markedly increased in hypothyroidism; in males from 169.5 +/- 20.3 to 834.0 +/- 82.2 pg/mg protein, and in females (whose pituitary PRL had been similarly reduced) from 103.1/I +/- 34.1 to 771.6 +/- 100.9 pg/mg protein. Serum PRL was significantly reduced in hypothyroid males (7.4 +/- 1.6 vs. 28.9 +/- 12.2 ng/ml) whereas in females, serum PRL was not significantly altered (41.4 +/- 11.6 vs. 38.8 +/- 14.3 ng/ml). The effect of hypothyroidism was reversed by administration of T4 in physiological doses. The authenticity of pituitary immunoreactive VIP was further established by demonstrating chromatographic patterns by Sephadex G-50 gel exclusion and reverse phase HPLC separations identical to synthetic VIP. Immunohistochemically reactive VIP cells could not be demonstrated in normal pituitaries, but the marked increase in VIP in hypothyroid animals made it possible to visualize a population of VIP immunoreactive stellate cells which appear to be distinct from hypothyroid lactotropes and thyrotropes.

Ultradian rhythm of growth hormone secretion in unrestrained, conscious male rabbits: role of endogenous somatostatintdagger.

Abstract The profiles of growth hormone (GH) secretion were examined by obtaining serial blood samples every 15 min for a 5 to 24 h observation period from freely-moving, conscious male rabbits chronically implanted with a right atrial cannula. The effects of restraint or surgical stress on GH secretion were also investigated in these animals. Four days after cannulation of the right atrium, plasma GH levels remained low without oscillation, during a 5 h observation period (1100 to 1600 h) with the mean (+/- SEM) value of 1.6+/-0.2 ng/ml. Individual rabbits exhibited a spontaneous, pulsatile GH secretion 7 days after the surgery. Mean 6 h GH levels were 5.6 +/- 0.8 ng/ml at 7 days after the surgery, 6.3 +/- 0.6 ng/ml at 14 days and 7.0 +/- 1.2 ng/ml at 28 days. Therefore, the animals, 7 to 14 days after cannulation, were used to analyse the pulsatile pattern of GH secretion throughout 6 to 24 h. Two episodes of 45 min immobilization stress, separated by 75 min, caused a complete suppression of the spontaneous GH secretion (mean 6 h GH levels, 2.2 +/- 0.1 ng/ml vs control, 5.0 +/- 0.5 ng/ml, P<0.01). No surges appeared after the first restraint stress. In 14 non-treated rabbits, plasma GH levels fluctuated in an episodic manner throughout the study with the peaks of 14.2 + 0.7 ng/ml, the nadirs of 2.6 +/- 0.2 ng/ml and the peak to peak intervals of 2.20 +/- 0.17 h. The iv administration of normal goat lambda-globulin (NGG) affected neither GH secretory patterns nor baseline levels of plasma GH. In contrast, the iv administration of anti-sornatostatin goat lambda-globulin (ASG) caused a significant increase in the amplitude of plasma GH peaks (38.8+/-1.9 vs NGG-treated, 13.7 +/- 0.8 ng/ml, P<0.001) as well as the trough level (13.5 +/- 0.6 vs NGG, 2.9 +/- 0.1 ng/ml, P<0.001) during a 24 h observation period. Also, ASG treatment increased numbers of plasma GH peaks per day (18.8+/-2.7 vs NGG, 12.2 +/- 0.8, P < 0.05) with concomitant shortening of the peak to peak interval (1.25 +/- 0.10 vs NGG, 2.03+/-0.12h, P<0.01). These findings suggest: 1) that GH is episodically secreted throughout the day in conscious male rabbits, 2) that surgical and restraint stresses suppress the spontaneous GH secretion, and 3) that endogenous somatostatin might rather play a tonic inhibitory role in GH release in conscious male rabbits, since ASG treatment resulted in sustained marked increases of plasma GH levels irrespective of the stage in GH pulsatile rhythm.

Localization of vasoactive intestinal peptide and peptide histidine isoleucine immunoreactivity and mRNA within the rat suprachiasmatic nucleus.

The distribution of vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) mRNA within the suprachiasmatic nucleus (SCN) of rats was evaluated by immunocytochemistry and in situ hybridization. The pattern of VIP and PHI immunoreactivity corresponded closely to the distribution of VIP/PHI mRNA within the ventrolateral SCN. Clear hybridization signal was observed within the SCN of rats killed 5 h after light onset and in rats killed 2 h after the onset of the dark phase of the light-dark cycle. Visual examination of the grain density within the autoradiographs suggested that VIP/PHI mRNA may occur in higher concentrations shortly after the onset of darkness than 5 h after the onset of the light phase.

Light selectively alters vasoactive intestinal peptide and peptide histidine isoleucine immunoreactivity within the rat suprachiasmatic nucleus.

The concentration of vasoactive intestinal peptide (VIP)-, peptide histidine isoleucine (PHI)-, neurotensin (NT)- and substance P (SP)-like immunoreactivity (LI) within the suprachiasmatic nucleus (SCN) were determined by radioimmunoassay in rats housed in LD 14:10 h, constant light or constant dark. No day-night differences were observed in the concentration of VIP-, PHI-, NT- or SP-LI within the SCN. Exposure to constant light significantly depressed the SCN concentrations of VIP- and PHI-LI, but had no significant effects on SCN concentrations of NT- or SP-LI, or VIP- or PHI-LI concentrations within the cortex. These data represent the first evidence that VIP/PHI-containing neurons may be involved in mediating photic information within the SCN.

Paraventricular nucleus mediates prolactin secretory responses to restraint stress, ether stress, and 5-hydroxy-L-tryptophan injection in the rat.

The role of the paraventricular nucleus (PVN) in mediating acute stimulatory PRL responses was investigated in conscious male rats. Electrolytic lesions, verified histologically at autopsy, were stereotaxically made in the PVN region, and sham lesions were made in control rats. Blood was obtained through a chronically indwelling catheter in the right atrium. PVN-lesioned (PVL) rats showed significantly lower T3 levels 1 week after surgery (less than 34.4 ng/dl) compared with sham (mean +/- SEM, 91.2 +/- 5.0 ng/dl) and intact (86.8 +/- 2.0 ng/dl) animals, verifying a lesion in the PVN. T3 was restored to normal (95.6 +/- 1.8 ng/dl) by daily sc administration of T4 (10 micrograms/kg BW) for at least 4 days before the day of the experiments. Basal PRL levels in PVL rats did not differ significantly from those in control or sham-lesioned animals. In response to restraint stress, plasma PRL levels of PVL rats did not rise, in contrast to marked elevation in PRL in sham and intact rats [PRL levels (mean +/- SEM; nanograms per ml), basal to peak: PVL, 4.3 +/- 0.3 to 4.5 +/- 0.4; sham, 4.5 +/- 0.5 to 47.0 +/- 4.1; intact, 4.0 +/- 0.3 to 46.3 +/- 4.9]. PVL also resulted in the complete inhibition of PRL secretion induced by 30-min inhalation of ether (basal to peak: PVL, 3.3 +/- 0.3 to 4.5 +/- 0.2; sham, 5.7 +/- 0.8 to 19.9 +/- 0.9; intact, 3.3 +/- 0.4 to 27.9 +/- 4.0). The stimulatory effect on plasma PRL in sham and intact rats by one iv bolus injection of the serotonin precursor 5-hydroxy-L-tryptophan (5-HTP; 10 mg/kg BW) was completely abolished in PVL animals (basal to peak: PVL, 3.7 +/- 0.6 to 5.2 +/- 1.4; sham, 6.7 +/- 0.6 to 36.0 +/- 0.5; intact, 4.1 +/- 1.2 to 33.3 +/- 3.2). In contrast to the marked alteration in PRL regulation, PVL rats exhibited a typical ultradian rhythm of plasma GH secretion during a 6-h observation period and increased release of GH induced by iv injection of 5-HTP [GH (nanograms per ml), basal to peak; PVL, 4.5 +/- 0.6 to 21.0 +/- 4.9; sham, 3.7 +/- 0.3 to 18.4 +/- 4.4; intact, 2.9 +/- 0.1 to 17.8 +/- 3.5]. These findings indicate that PRL responses to stress and to serotonin act through the PVN, the site of origin of several putative PRL-releasing factors.(ABSTRACT TRUNCATED AT 400 WORDS)

Regional distribution of gastrin-releasing peptide- and somatostatin-like immunoreactivity in the rabbit hypothalamus.

Regional distribution of gastrin-releasing peptide- (GRP) and somatostatin (SRIF)-like immunoreactivity in the discrete nuclei of the hypothalamus was examined in the rabbit according to Palkovits' microdissection method. GRP-like immunoreactivity (LI) was detected abundantly in the hypothalamus as compared with the cerebral cortex when measured by radioimmunoassay using the antiserum recognizing the C-terminal portion of synthetic porcine GRP. On gel-filtration chromatography of the hypothalamic extracts, two major peaks of GRP-LI were eluted; the peak with larger molecular size corresponded to synthetic porcine GRP1-27 and the smaller size to porcine GRP14-27. A concentration of GRP-LI was highest in the infundibular nuclei (IFN) as well as the ventromedial nuclei (VMN), and next high in the paraventricular nuclei (PVN), suprachiasmatic nuclei (SCN) and periventricular nuclei (PEV). The content of GRP-LI in the median eminence was not so much when compared with them. On the other hand, SRIF was localized in the highest concentration in the ME, followed by the VMN and IFN, as well as the PEV. The findings indicate that porcine GRP-LI exists in the hypothalamus of rabbits with characteristic regional distribution. Concurrent localization of GRP-LI and SRIF in some parts of the hypothalamus may suggest the interaction of both peptides in these areas under various physiological and pathological status.

Effect of various catecholamine antagonists on prolactin secretion in conscious male rabbits.

To clarify physiological roles of catecholaminergic systems in the control of rabbit prolactin (PRL) release, the effect of various catecholamine receptor antagonists on plasma PRL levels was examined in conscious, freely moving male rabbits. An intravenous (iv) injection of yohimbin (2.5 mg/kg body wt), an alpha 2-adrenoreceptor antagonist, but not prazosin (2 mg/kg body wt), an alpha 1-adrenergic receptor antagonist, resulted in a significant elevation of plasma PRL. Conversely, propranolol (2.5 mg/kg body wt, iv), a nonselective beta-adrenoreceptor antagonist, and metoprolol (2.6 mg/kg body wt, iv), a beta 1-adrenergic antagonist, slightly but significantly suppressed basal levels of plasma PRL. On the other hand, haloperidol (0.5 mg/kg body wt, iv), pimozide (0.3 mg/kg body wt, iv), sulpiride (5 mg/kg body wt, iv), chlorpromazine (3 mg/kg body wt, iv), and YM-09151-2 (0.2 mg/kg body wt, iv), all dopamine receptor antagonists caused a significant increase in plasma PRL. These results suggest that dopaminergic and alpha 2-adrenergic mechanisms exert a tonic inhibitory role and beta-adrenergic mechanisms, probably beta 1, a tonic stimulatory role in the regulation of PRL release in the rabbit.

Inhibitory effect of [Asu1,7]-eel calcitonin on growth hormone-secretion in conscious, freely moving, male rats.

The effect of [Asu1,7]-eel calcitonin (ECT), which is an equipotent analog of eel calcitonin (CT), on GH secretion was investigated in freely moving conscious male rats. Pulsatile GH secretion was completely inhibited by iv injection of ECT (2.5 micrograms/rat). The mean 6-h plasma GH levels, 9.54 +/- 2.34 ng/ml (mean +/- SEM) in ECT-treated rats, were significantly lower than those in saline-treated rats (69.9 +/- 9.4 ng/ml, P less than 0.001). In order to examine the action of ECT on the central nervous system, 25 ng ECT dissolved in 10 microliters saline were injected into the lateral ventricle of conscious male rats. The bursts of GH secretion were completely abolished by this dose of intraventricularly (ivt) injected ECT. The mean 6-h GH levels 5.8 +/- 0.8 ng/ml, were also significantly lower than those in control rats (35.8 +/- 6.6 ng/ml, P less than 0.01). Serum Ca levels did not change after the ivt injection of 25 ng ECT but fell significantly after the iv injection of 2.5 micrograms ECT. In order to clarify the inhibitory mechanism of GH secretion by ECT, the effect of ECT on the release of GH elicited by prostaglandin E1 (PGE1), a well-known GH secretagogue acting directly on the pituitary, was examined in vivo as well as in vitro. Both ivt (2.5, 25, or 250 ng/10 microliters X rat) and iv (2.5 or 25 micrograms/rat) injections of ECT caused a significant and dose-dependent suppression of PGE1-induced GH rises in conscious rats. In contrast, 10(-8) to 10(-7) M ECT failed to affect the baseline secretion of GH and its release by 5 X 10(-6) M PGE1 from rat anterior pituitary tissues perifused in vitro. These findings suggest that ECT suppresses GH secretion in the rat, at least in part, through the central nervous system.

Effect of [Asu1,7]eel calcitonin on prolactin release in normal subjects and patients with prolactinoma.

The effect of [Asu1,7]eel calcitonin (ECT), an equipotent analogue of eel CT, on prolactin (Prl) secretion was examined in 12 healthy male subjects and in 6 patients with prolactinoma. In healthy subjects, ECT (0.5 microgram/kg body weight . h) or saline was infused for 2 h and TRH was injected iv as a bolus of 500 micrograms at 1 h of ECT or saline administration. ECT did not affect basal Prl levels during 1 h of infusion. TRH caused a significant increase of plasma Prl with peak values of 75.2 +/- 11.6 ng/ml in ECT-infused subjects, which did not differ from those infused with saline (68.5 +/- 8.3 ng/ml). Next, an iv bolus injection of regular insulin (0.1 U/kg body weight) was followed by an infusion of ECT or saline alone. Plasma Prl peaks after hypoglycaemic stress were significantly lower in ECT-infused subjects than those in saline-injected controls (ECT, 16.5 +/- 3.1 vs 33.5 +/- 9.6 ng/ml, P less than 0.05). In patients with prolactinoma, basal levels of plasma Prl ranging from 42.0-4130 ng/ml failed to change during iv infusion of ECT. Moreover, ECT (10(-9) - 10(-6)M) did not affect Prl release from prolactinoma tissues perifused in vitro. These findings suggest that ECT may not act directly on the pituitary to modify Prl release. Rather, peripherally administered ECT appears to suppress Prl release via the central nervous system.

Idiopathic growth hormone (GH) deficiency, and GH deficiency secondary to hypothalamic germinoma: effect of single and repeated administration of human GH-releasing factor (hGRF) on plasma GH level and endogenous hGRF-like immunoreactivity level in cerebrospinal fluid.

Plasma GH responses to iv administered synthetic human GH-releasing factor-(1-44)-NH2 (hGRF) and the concentration of endogenous hGRF-like immunoreactivity (hGRF-LI) in the cerebrospinal fluid (CSF) were examined in 16 children with GH deficiency (GHD). Ten patients had idiopathic GHD, and six had GHD secondary to germinoma. An iv bolus hGRF (1 microgram/kg BW) injection test was performed the day before and the day after treatment, with a daily 1-h iv infusion of hGRF (2 micrograms/kg BW) for 3 days. Plasma GH increases (greater than 5 ng/ml) after the first iv bolus injection of hGRF occurred in 2 of the 10 idiopathic GHD children and in 4 of the 6 GHD patients with germinoma whereas the first bolus hGRF injection failed to elicit GH release in the remaining 10 patients. The mean +/- SEM peak plasma GH level after the first bolus hGRF dose in the patients with germinoma (8.2 +/- 2.2 ng/ml) was significantly higher than that in the idiopathic GHD patients (2.9 +/- 0.9 ng/ml; P less than 0.05), but significantly lower than that in normal children with short stature (18.5 +/- 2.5 ng/ml; P less than 0.05). In the 2 patients with germinoma and in 5 of the 8 idiopathic GHD children who did not respond to the first hGRF bolus dose, a significant plasma GH response to hGRF occurred during a daily iv infusion of hGRF for 3 consecutive days, whereas the remaining 3 idiopathic GHD children failed to respond to the daily hGRF infusions. The plasma GH response after the second hGRF bolus dose given after treatment with daily hGRF infusions for 3 days was not different from that after the first hGRF bolus in patients with germinoma or that in the idiopathic GHD children. hGRF-LI was not detected (less than 5.8 pg/ml) in the CSF in any of 5 patients with germinoma, whereas it was present in 5 idiopathic GHD patients (mean, 17.5 +/- 0.9 pg/ml), 3 of whom were nonresponders to daily hGRF infusions. From these results, GHD secondary to destruction of hypothalamic GRF neurons might be defined by the following findings: 1) lack of a GH response to the standard provocative tests acting through the hypothalamus; 2) significant increase in plasma GH after a single bolus and/or repetitive iv administration of hGRF; and 3) undetectable or extremely low levels of endogenous hGRF-LI in the CSF. Most of the idiopathic GHD patients responded to the repetitive hGRF infusion, suggesting insufficient secretion of hypothalamic hGRF as the primary defect. However, since hGRF-LI was detectable in the CSF in some of the idiopathic GHD patients, its pathogenesis must be multifactorial.

Presence of growth hormone-releasing factor-like immunoreactivity in human cerebrospinal fluid.

Immunoreactive human growth hormone-releasing factor (I-hGRF) in human cerebrospinal fluid (CSF) was measured by radioimmunoassay using antiserum specific to the C-terminal portion of hGRF(1-44)NH2. Dilution curves of I-hGRF in the CSF were completely parallel to that of synthetic hGRF(1-44)NH2 standard. On Sephadex G-50 column chromatography a single peak of I-hGRF in the CSF was eluted at the position of synthetic hGRF(1-44)NH2. I-hGRF was present in the CSF of all control patients without any endocrine disease (mean +/- SE, 29.3 +/- 2.0 pg/ml) whereas I-hGRF in the CSF was not detectable (less than 5.8 pg/ml) in any of the patients with hypothalamic germinoma. In all patients with idiopathic GH deficiency, I-hGRF in the CSF was measurable but its concentration (15.1 +/- 1.0 pg/ml) was significantly (p less than 0.05) lower than that in the control subjects. No difference in I-hGRF levels of the CSF was observed between patients with acromegaly and control subjects. These findings demonstrate for the first time that I-hGRF is present in human CSF. Measurement of I-hGRF in the CSF may be useful for understanding the pathophysiology of hypothalamo-pituitary diseases.

Regional distribution of rat growth hormone releasing factor-like immunoreactivity in rat hypothalamus.

A heterologous RIA for rat GH-releasing factor (rGRF) was established using synthetic rGRF-(1-43)OH for both standard reference and radioiodination with the antiserum produced against human GRF-(1-44) NH2. The regional distribution of rGRF-like immunoreactivity (LI) in rat hypothalamus was examined according to the Palkovits microdissection method and compared with that of somatostatin (SRIF)-LI. Both rGRF- and SRIF-LI contents (mean +/- SE; nanograms per mg protein) were highest in the median eminence (rGRF, 32.28 +/- 11.42; SRIF, 109.9 +/- 19.2) and next most abundant in the arcuate nucleus (rGRF, 3.50 +/- 0.47; SRIF, 12.88 +/- 0.60). Only a small amount of rGRF-LI was found in the ventromedial (1.41 +/- 0.51) and dorsomedial (1.16 +/- 0.15) nuclei and the anterior hypothalamic area (1.29 +/- 0.42), whereas rGRF-LI was not detected in the other nuclei of the hypothalamus. A considerable amount of SRIF-LI was contained in the periventricular, ventromedial, and paraventricular nuclei and the anterior hypothalamic area, in accordance with other reports. Gel filtration chromatography revealed that hypothalamic extracts contained a major peak of rGRF-LI corresponding to rGRF-(1-43)OH and two peaks of SRIF-LI equivalent to SRIF-(1-28) and SRIF-(1-14), respectively. These findings indicate that rGRF-LI is localized in the median eminence and arcuate nucleus in the rat and that rGRF-, SRIF-(1-28)-, and SRIF-(1-14)-LI are present in a 1:2.10:6.29 ratio on a molar basis.

Stimulatory effect of peptide histidine isoleucine amide 1-27 on prolactin release in the rat.

Intravenous injection of pure peptide histidine isoleucine amide 1-27 (PHI) resulted in a prompt and significant increase of plasma prolactin (PRL) in conscious freely-moving male rats. Using a perifusion system of rat anterior pituitary tissues in vitro, effluent PRL levels were also increased by 10(-8)-10(-7) M PHI. A PRL releasing potency of PHI was almost similar with that of vasoactive intestinal polypeptide (VIP) or TRH both in vivo and in vitro. Coupled with the recent immunocytochemical studies showing the dense network of PHI immunoreactive fibers around the hypophysial portal vessels, PHI might be another candidate for PRL releasing factor.

Noradrenergic modulation of human pancreatic growth hormone-releasing factor (hpGHRF1-44)-induced growth hormone release in conscious male rabbits: involvement of endogenous somatostatin.

To clarify the role of noradrenergic neurons in the regulation of GH secretion, the effects of iv administered noradrenergic antagonists were investigated in freely moving, conscious male rabbits. During a 6-h observation period (1030-1630 h), control rabbits manifested pulsatile GH secretion with surges between 1030-1200 and 1415-1630 h. Phenoxybenzamine, (POB), an alpha-adrenergic blocker (5 mg/kg, twice), abolished the episodic GH surges; propranolol, a beta-adrenergic blocker (2.5 mg/kg, twice), did not. The bolus injection (1 or 10 micrograms) of synthetic human pancreatic GH-releasing factor (hpGHRF) with 44 amino acid residues (hpGHRF1-44) resulted in significant rises in the plasma GH of control animals. The plasma GH responses to hpGHRF1-44 were significantly larger in propranolol-treated than control rabbits. In contrast, POB completely suppressed the hpGHRF1-44-induced GH release. The injection of antisomatostatin (SRIF) serum into POB-treated rabbits did not yield a disinhibition of the episodic GH surges but restored the plasma GH rises after hpGHRF1-44 injection. These results indicate that noradrenaline++ plays an important role in regulating GH secretion in the rabbit. We propose that alpha-noradrenergic blockade suppresses GH release not only by inhibiting the release of hypothalamic GHRF but also by stimulating the secretion of SRIF and that beta-noradrenergic blockade enhances GH release by inhibiting the release of SRIF from the hypothalamus.

Stimulation of growth hormone by vasoactive intestinal polypeptide in acromegaly.

Vasoactive intestinal polypeptide (VIP) was administered as an iv bolus of 1 micrograms/kg BW to 8 acromegalic patients and in doses of 0.5 and 1 microgram/kg BW to 15 normal volunteers. Both systolic and diastolic blood pressures decreased, and pulse rate increased transiently after VIP injection. VIP stimulated PRL release from the anterior pituitary in normal subjects. Plasma PRL responses to VIP in women were dose dependent and larger than those in men. On the other hand, plasma GH levels rose markedly after VIP injection in all 6 patients with untreated acromegaly. In 2 patients studied after transsphenoidal microadenomectomy, there was no plasma GH response to VIP. In 2 other patients with inactive acromegaly as well as in normal subjects, VIP failed to affect plasma GH levels. In all 6 patients with active acromegaly, LRH (1-2 micrograms/kg BW, iv) did not increase plasma GH levels, but TRH (5-10 micrograms/kg BW, iv) caused significant increases in plasma GH, the magnitude of which was not similar to that of increases seen after VIP injection. Paradoxical GH responses to TRH were not observed in patients in the inactive phase after transsphenoidal surgery. These findings suggest that VIP stimulates GH release in vivo in acromegalic patients. A VIP test as well as a TRH test offer promise as simple and reliable techniques to evaluate the activity of acromegaly, particularly after transsphenoidal surgery.