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

The effects of alpha 1-adrenergic agents on GH release and intracellular free Ca2+ concentration ([Ca2+]i) were investigated in purified rat somatotroph preparations. Phenylephrine (PHE) stimulated in vitro GH release; the maximal effect (2.5-fold stimulation) occurred at 1 microM PHE. The effect was completely blocked by the alpha-adrenergic antagonist phentolamine and partially counteracted by the beta-antagonist propranolol. Experiments with the fluorescent Ca2+ probe fura 2 show that PHE causes [Ca2+]i to rise from 178 +/- 31 nM (mean +/- SE; n = 25) to 370 +/- 55 nM (n = 9). This effect was complete within 20 sec and was maintained for at least 5-10 min. The rise was rapidly interrupted by administration of 1 microM phentolamine. The beta-receptor agonist isoproterenol caused a small [Ca2+]i rise due to action on alpha 1-adrenoreceptors. The PHE-induced [Ca2+]i rise showed two components: an initial peak due to Ca2+ mobilization from intracellular stores and a subsequent rise due to Ca2+ influx from the extracellular space. Somatostatin (SRIF) lowered both resting [Ca2+]i and Ca2+ influx stimulated by PHE. Pertussis toxin pretreatment did not modify PHE-induced [Ca2+]i changes, while it completely prevented the effect of SRIF on both resting and triggered [Ca2+]i, thus suggesting that a GTP-binding protein sensitive to the toxin is involved in the transduction of SRIF action. The increase in cAMP induced by cholera toxin pretreatment modified neither PHE nor SRIF action on [Ca2+]i. In conclusion, in rat somatotrophs Ca2+ mobilization and influx are stimulated by alpha 1-adrenergic agents, and this triggered [Ca2+]i rise results in a stimulation of GH release. In these cells SRIF is able to reduce both resting [Ca2+]i levels and [Ca2+]i increases induced by alpha 1-adrenergic activation.
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PMID:Alpha 1-adrenergic stimulation of in vitro growth hormone release and cytosolic free Ca2+ in rat somatotrophs. 289 97

Somatostatin (SS) and noradrenaline (NA) are distributed in the rat cerebral cortex, and seizure activity is one of the aspects of behavior affected by both neurotransmitters. Due to the possible interaction between both neurotransmitter systems, we studied whether phenylphrine, an alpha 1-adrenoceptor agonist, and prazosin, an alpha 1-adrenoceptor antagonist, can modulate SS-like immunoreactivity (SS-LI) levels, binding of [125I][Tyr11]SS to its specific receptors, the ability of SS to inhibit adenylate cyclase (AC) activity, and the guanine nucleotide binding regulatory protein G, and G., in the Sprague-Dawley rat frontoparietal cortex. An IP dose of 2 or 4 mg/kg of phenylephrine injected 7 h before decapitation decreased the number of SS receptors and increased the apparent affinity in frontoparietal cortex membranes. An IP dose of 20 or 25 mg/kg of prazosin administered 8 h before decapitation increased the number of SS receptors and decreased their apparent affinity. The administration of prazosin before the phenylephrine injection prevented the phenylephrine-induced changes in SS binding. The addition of phenylephrine and/or prazosin 10(-5) M to the incubation medium changed neither the number nor the affinity of the SS receptors in the frontoparietal cortex membranes. Phenylephrine or prazosin affected neither SS-LI content nor the basal or forskolin (FK)-stimulated AC activities in the frontoparietal cortex. In addition, SS caused an equal inhibition of AC activity in frontoparietal cortex membranes of phenylephrine-and prazosintreated rats compared with the respective control group. Finally, phenylephrine and prazosin did not vary the pertussis toxin (PTX)-catalyzed ADP ribosylation of Gi- and/or Go-proteins. These results suggest that the above-mentioned changes are related to the phenylephrine activation of alpha 1-adrenoceptors or to the blocking of these receptors by prazosin. In addition, these data provide further support for a functional interrelationship between the alpha 1-adrenergic and somatostatinergic systems in the rat frontoparietal cortex.
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PMID:Effect of phenylephrine and prazosin on the somatostatinergic system in the rat frontoparietal cortex. 874 58

1. We have investigated the actions of the somatostatin analogue octreotide in the portal hypertensive Wistar rat in vivo and in rat small mesenteric artery and aorta in vitro. 2. In small mesenteric artery, octreotide (0.1-0.3 microM) failed to produce any direct contraction, nor did it affect contractions to noradrenaline (NA, 10 microM) or endothelium-dependent relaxations to acetylcholine. 3. In rat aorta, octreotide (0.3 microM) and somatostatin (1 microM) failed to affect contractions to NA (1 microM), or concentration-contractile response curves to NA. 4. In rat vas deferens, octreotide and somatostatin significantly reduced contractile responses to electrical stimulation with pD2 values (-log IC50) of 8.19 +/- 0.10 (n = 4) and 8.16 +/- 0.26 (n = 4), respectively. Hence, the lack of effect of these agents in aorta or mesenteric artery was not due to lack of efficacy or inappropriate choice of concentration. 5. In the anaesthetized portal hypertensive rat, intravenous injection of octreotide (1-100 microg kg[-1]) did not significantly affect systemic blood pressure, nor did it affect mesenteric vascular conductance as measured by laser doppler flow probes. However, octreotide (100 microg kg[-1]) significantly reduced vascular conductance to 74.2 +/- 7.7% of control (n = 6) in porto-systemic shunt vessels as measured by laser doppler flow probes. 6. Phenylephrine (1 microg kg[-1]) significantly raised blood pressure and significantly decreased vascular conductance in both mesenteric (66.6 +/- 3.7% of control) and porto-systemic shunt vessels (58.7 +/- 10.0% of control). 7. It was concluded that octreotide has selective effects on porto-systemic shunt vessles in vivo in the portal hypertensive rat.
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PMID:Vascular actions of octreotide in the portal hypertensive rat. 937 66