Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P61278 (somatostatin)
 22,083 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Pituitary tumors from 376 patients were investigated, using immunocytochemical techniques at the light and electron microscopic level, and autoradiography combined with immunocytochemistry for localizing somatostatin (SRIH) receptors. Prolactinomas, growth hormone-secreting adenomas causing acromegaly, and hormonally inactive adenomas were most frequently observed (153, 86, and 90 tumors, respectively). Among the latter, we could distinguish "alpha-only adenomas," many of which were oncocytomas. At the light and electron microscopic levels, cells containing (and presumably producing) simultaneously both prolactin and growth hormone, and cells containing exclusively either prolactin or growth hormone, could be demonstrated. In addition, a highly variable number and distribution of SRIH receptors could be shown in tumors secreting prolactin, growth hormone, and in tumors not associated with symptoms caused by inappropriate hormone secretion. The systematic combination of clinical, radiological, and biological techniques has currently brought great progress in the behavior and therapeutic concepts of pituitary lesions, and promises new achievements in the near future.
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PMID:Immunocytochemistry of pituitary tumors. 244 Sep 42

The dog pituitary pars intermedia (PI) appears to consist of relative large numbers of ACTH-containing cells in addition to the more abundant alpha MSH-containing cells. Since regulation of PI secretion probably varies across mammalian species, this study was undertaken to identify substances potentially involved in the control of dog PI POMC peptide secretion and to determine if these substances altered the secretion of immunoreactive (IR) ACTH and IR-alpha MSH in a parallel fashion. Pituitary neurointermediate lobes from dogs were collected and dispersed, and the PI cells obtained were perifused. For comparison, rat PI and pars distalis (PD) cells as well as dog PD cells were similarly collected and perifused. Dog PI cells secreted IR-alpha MSH at a basal rate of 125 +/- 59 (mean +/- SD) pg/min.10(5) cells and IR-ACTH at a rate of 40 +/- 9 pg/min.10(5) cells (molar IR-alpha MSH/IR-ACTH = 10). In contrast, secretion rates for IR-alpha MSH and IR-ACTH from perifused rat PI cells were 171 +/- 108 and 3 +/- 2 pg/min.10(5) cells, respectively (molar IR-alpha MSH/IR-ACTH = 179). Using Sephadex G-50 gel filtration chromatography, virtually all of the IR-beta-endorphin secreted by dog PI cells eluted near beta-endorphin (1-31). In addition, all of the IR-alpha MSH secreted by dog PI cells coeluted with synthetic alpha MSH on the G-50 column, but IR-ACTH appeared in two peaks, one eluting near porcine ACTH-(1-39) and another, apparently larger mol wt species. Dopamine and somatostatin were found to inhibit the secretion of IR-alpha MSH and IR-ACTH from perifused dog PI cells in a parallel and dose-dependent fashion. Norepinephrine and epinephrine similarly inhibited POMC peptide secretion, but this effect was blocked by haloperidol, suggesting that it was mediated through a dopamine receptor. CRF stimulated the secretion of both hormones from dog PI, and this effect was abolished by treatment of the cells with either dopamine or somatostatin. Cortisol had no effect on either basal or CRF-stimulated secretion of IR-alpha MSH or IR-ACTH from dog PI cells, but it did inhibit CRF-stimulated IR-ACTH from perifused dog PD. These results suggest that 1) dog PI secretes considerably more IR-ACTH than that in the rat; 2) the probable separate cell sources of IR-alpha MSH and IR-ACTH in dog PI are regulated in an identical fashion; and 3) dopamine, somatostatin, and CRF may function in the physiological or pathophysiological regulation of dog PI.
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PMID:Regulation and secretion of proopiomelanocortin peptides from isolated perifused dog pituitary pars intermedia cells. 253 71

Pituitary GH secretion is regulated by a delicate interplay between stimulatory (GRF) and inhibitory [somatostatin (SRIF)] hypothalamic hormones, although the nature of the GRF/SRIF interaction remains to be elucidated. In the present study, we documented a significant elevation of plasma SRIF-like immunoreactivity in 72-h fasted rats compared to that in fed controls (129.0 +/- 17.9 vs. 38.2 +/- 5.8 pg/ml; P less than 0.01) and used this model of high SRIF tone to further delineate the interrelation between GRF and SRIF in physiological regulation of pulsatile GH secretion. We examined pituitary GH responsiveness to GRF, both in vivo and in vitro, after 72-h exposure to nutritional deprivation and high SRIF secretion. In vivo, GRF-induced GH release was markedly enhanced in the face of high circulating SRIF; freely moving, starved rats released 4- to 8-fold more GH than fed controls in response to rat GRF iv. In vitro, both basal and human GRF-induced GH release were augmented 2- to 4-fold in perifused dispersed anterior pituitary cells of starved rats compared to those in fed controls, and this enhanced responsiveness persisted in the presence of 10(-9) M SRIF. These results demonstrate that SRIF not only inhibits GH secretion stimulated by GRF, but that under different temporal conditions SRIF may act in a paradoxically positive manner to sensitize pituitary GH responsiveness to GRF. Such a cooperative interaction of the two peptides may be necessary to optimize pulsatile GH release. Our findings provide support for the hypothesis that the temporal patterning of hypothalamic GRF/SRIF signals to pituitary somatotrophs may be the major determinant for pulsatile GH secretion and, ultimately, body growth.
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PMID:Paradoxical enhancement of pituitary growth hormone (GH) responsiveness to GH-releasing factor in the face of high somatostatin tone. 256 83

The long-acting somatostatin analogue SMS 201-995 has been shown to be efficient in the treatment of somatotropic and thyrotropic adenomas. In some cases, it can suppress adenoma secretion and lead to tumor shrinkage. Pituitary macroadenomas are often associated with a vision-threatening chiasmal syndrome. In this series, SMS 201-995 was administered subcutaneously to eight patients with pituitary macroadenomas of various types responsible for severe long-lasting visual defects. An obvious improvement of both visual fields and acuity occurred in six patients, in two of these during the first 4 to 6 hours of treatment; in two patients, gonadotropic adenomas were unresponsive. Maximal improvement (normalization of visual fields in three cases) occurred within 6 to 45 days and was sustained during the 1- to 12-month follow-up period. This effect seems independent of the type of adenoma since the adenomas secreting growth hormone (GH) and thyroid-stimulating hormone and silent corticotropic-secreting adenomas responded as well as did two of the non-functioning adenomas. In one acromegalic patient visual improvement was obtained while the abnormal GH secretion remained unaltered. In all cases but one, no tumor shrinkage could be demonstrated. These data demonstrate that SMS 201-995 can rapidly improve the chiasmal syndrome due to pituitary macroadenoma, and suggest that this effect might be independent of a reduction in tumor volume.
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PMID:The effect of somatostatin analogue on chiasmal dysfunction from pituitary macroadenomas. 280 22

Pituitary content and concentration of growth hormone was significantly reduced, and hypothalamic somatostatin content significantly increased, in old constant estrous as compared to young female rats. Increased levels of somatostatin may contribute to the decrease in pituitary growth hormone levels in these animals.
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PMID:Pituitary growth hormone and hypothalamic somatostatin in young female rats versus old constant estrous female rats. 286 5

Although aromatase activity is exceptionally high in the teleost pituitary, it is not known which of the secretory cell types are responsible. Pituitary glands from the longhorn sculpin (Myoxocephalus octodecimspinosus) were sectioned transversely into "cephalic" and "caudal" fragments and cultured for 24 hr in medium containing [7-3H]androstenedione. Radiolabeled estrone and estradiol-17 beta production were measured as an estimate of aromatization. In order to determine the distribution pattern of different cell types, the in situ pituitary and dissected fragments were analyzed by standard cytological procedures. Further verification of cell function was obtained by somatostatin (SRIF) and corticotropin-releasing factor (CRF) immunocytochemistry. Estrogen yields obtained from caudal fragments in two separate experiments averaged four times higher per milligram protein than yields from matched cephalic fragments. In addition, female glands synthesized significantly more estrogen than those of males. Due to an anteroflexion of the longitudinal axis and a disposition of the gonadotropic (GTH) cells at the periphery of the gland and surrounding the neurointermediate lobe (NIL), the classical subdivisions of the teleost adenohypophysis were not strictly applicable to the sculpin. The predominance of growth hormone (GH) secreting cells in the caudal fragment suggests their participation in aromatization, a finding which is consistent with a previous study of rodent pituitary; however, a role for gonadotropes and other hypophysial cells in this transformation cannot be ruled out.
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PMID:Distribution of cell types and aromatase activity in the sculpin (Myoxocephalus) pituitary. 286 48

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.
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PMID:Effect of hypothalamic ventromedial lesions on plasma growth hormone response to growth hormone-releasing factor in rats. 286 81

The relationship between basal and stimulated plasma GH and somatomedin-C (SmC) levels in acromegalic patients was evaluated. The basal plasma SmC levels of 66 patients were significantly correlated (P less than 0.01) with mean daily plasma GH levels, but not with the percent GH increase after GH-releasing hormone or TRH or the GH decrease after acute bromocriptine administration. Bromocriptine (7.5-15 mg/day) administration for 9.2 +/- 0.9 (+/- SD) months in 20 patients significantly (P less than 0.05) decreased GH levels. SmC decreased significantly [from 9.8 +/- 1.9 to 5.1 +/- 0.7 U/ml (mean +/- SE)] only in the 10 patients who had the more marked GH inhibition. The administration of a somatostatin analog, SMS 201-995 (100 micrograms twice daily), to 12 patients for 16 weeks significantly decreased plasma GH and SmC levels beginning on the second day of therapy; normal SmC levels were achieved in 5 of 12 patients. Pituitary adenomectomy resulted in normal GH and SmC levels in 10 of 12 and 8 of 12 patients, respectively. Our data indicate an overall dependency of plasma SmC levels on plasma GH levels in acromegaly, although similar GH levels may have differing somatomedin-stimulating activities. A derangement in the feedback mechanisms controlling GH secretion is indicated by the failure of elevated SmC levels to influence the GH responsiveness to releasing hormones. In evaluating pharmacological or surgical treatments of acromegaly, a single plasma SmC value can reliably replace several plasma GH determinations.
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PMID:Relationship between somatomedin-C and growth hormone levels in acromegaly: basal and dynamic evaluation. 287 7

Changes in DNA synthesis in lactotrophs of primary monolayer cultures of the rat pituitary cells were studied, using immunoperoxidase staining in combination with autoradiography. Pituitary cell cultures were treated for 3 days with thyroliberin (TRH), bromocriptine (CB154) or somatostatin (SRIF). The proportion of lactotrophs labelled with 3H-thymidine in the total pool of labelled cells served as a criterion for the estimation of DNA synthesis in prolactin-secreting cells. Prolactin secretion by the same cultures was measured by homologous radioimmunoassay. TRH (10 ng/ml) stimulated DNA synthesis in the total population of pituitary cells, but not in lactotrophs. SRIF decreased selectively the proliferation of lactotrophs, but failed to depress or even stimulated DNA synthesis in some cell types of the rat pituitary gland in the cultures. The quantitative method of studying DNA synthesis in anterior pituitary may be used to evaluate the effects of a number of biologically active compounds on various cell systems.
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PMID:[Regulation of hormonal secretion and DNA synthesis in the lactotrophs of the rat adenohypophysis in vitro in primary cell cultures]. 289 27

The role of GTP on somatostatin-induced K+ current increase was examined in dissociated human pituitary tumor cells obtained from three acromegalic patients. Pituitary cells in culture were voltage-clamped by using the patch clamp technique in the whole-cell configuration. Somatostatin (100 nM) increased the membrane permeability to K+ ions and inhibited hormone secretion. A current-voltage relation of the somatostatin-induced K+ current showed an inward rectification when the concentration of extracellular K+ ions was increased. The amplitude of the somatostatin-induced K+ current decreased during recording when the patch pipette solution did not contain GTP; addition of 100 microM GTP to the patch pipette solution prevented this reduction. Intracellular application of 100 microM guanosine 5'-[gamma-thio]triphosphate (GTP[gamma S] evoked an inward rectifying K+ conductance in the absence of somatostatin. After the GTP[gamma S]-induced K+ conductance reached a steady level, application of somatostatin did not further increase the K+ conductance. In pertussis toxin-treated cells GTP[gamma S] did not evoke K+ conductance. It was concluded that somatostatin-induced K+ channels were regulated by a GTP-binding protein.
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PMID:Requirement of GTP on somatostatin-induced K+ current in human pituitary tumor cells. 289 85


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