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)

Contracting muscle cells release K ions into their surrounding interstitial fluid, and some of these ions, in turn, enter venous plasma. Thereby, intense or exhaustive exercise may result in hyperkalemia and potentially dangerous cardiotoxicity. Training not only reduces hyperkalemia produced by exercise but in addition, highly conditioned, long-distance runners may show resting hypokalemia that is not caused by K deficiency. To examine the factors underlying these changes, dogs were studied before and after 6 wk of training induced by running on the treadmill. Resting serum [K] fell from 4.2 +/- 0.2 to 3.9 +/- 0.3 meq/liter (P less than 0.001), muscle intracellular [K] rose from 139 +/- 7 to 148 +/- 14 meq/liter (P less than 0.001), and directly measured muscle cell membrane potential (Em) in vivo rose from -92 +/- 5 to -103 +/- 5 mV (P less than 0.001). Before training, resting Em of isolated intercostal muscle in vitro was -87 +/- 5 mV, and after incubation in 10(-4) M ouabain, Em fell to -78 +/- 5 mV. After training, resting Em of intercostal muscle rose to -95 +/- 4, but fell to -62 +/- 4 mV during incubation in 10(-4) M ouabain. The measured value for the Em was not completely explained by the increased ratio of intracellular to extracellular [K] or by the potassium diffusion potential. Skeletal muscle sarcolemmal Na,K-ATPase activity (microM inorganic phosphate mg-1 protein h-1) increased from 0.189 +/- 0.028 to 0.500 +/- 0.076 (P less than 0.05) after training, whereas activities of Mg2+ -dependent ATPase and 5'nucleotidase did not change. In untrained dogs, exercise to the point of exhaustion elevated serum [K] from 4.4 +/- 0.5 to 6.0 +/- 1.0 meq/liter (P less than 0.05). In trained dogs, exhaustive exercise was associated with elevation of serum [K] from 3.8 +/- 0.3 to 4.2 +/- 0.4 (NS). The different response of serum [K] to exercise after training was not explainable by blood pH. Basal insulin levels rose from 7.0 +/- 0.7 microU/ml in the untrained dogs to 9.9 +/- 1.0 microU/ml (P less than 0.05) after training. Although insulin might have played a role in the acquired electrical hyperpolarization, the reduced exercise-produced hyperkalemia after training was not reversed by blockade of insulin release with somatostatin. Although the fundamental mechanisms underlying the cellular hyperpolarization were not resolved, our observations suggest that increased Na-K exchange across the sarcolemmal membrane, the increase of Na,K-ATPase activity and possibly increased electrogenicity of the sodium pump may all play a role in the changes induced by training.
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PMID:Muscle cell electrical hyperpolarization and reduced exercise hyperkalemia in physically conditioned dogs. 298 19

Somatostatin binding and the ability to inhibit cyclic AMP stimulated protein kinase were investigated utilizing isolated pancreatic islets, anterior pituitary plasma membranes, adipocytes, erythrocyte ghosts, hepatic plasma membranes, and anterior pituitary secretion vesicles. Three types of response were observed. With type I response, somatostatin bound specifically to pancreatic islets and anterior pituitary secretion vesicles and inhibited cyclic AMP stimulated protein kinase. In type II response, adipocytes and anterior pituitary plasma membranes exhibited somatostatin binding but no effect of the ligand on the kinase. In erythrocyte membrane ghosts and hepatic plasma membranes, there was neither specific somatostatin binding nor protein kinase inhibition (type III response). The absence of somatostatin binding in erythrocytes or hepatic plasma membranes cannot be explained by degradation of the ligand per se. Secretory vesicles isolated from the anterior pituitary gland bind somatostatin with an average affinity which exceeds that observed in plasma membrane (for pituitary secretory vesicles Kd1 = 8.5 X 10(-8)M, Kd2 = 5.2 X 10(-7)M; for pituitary membranes Kd1 = 1.9 X 10(-8)M, Kd2 = 8.1 X 10(-7)M). The molar concentration of high affinity binding sites (Ro) for plasma membranes was 6.9 X 10(-10)M; for secretory vesicles 3.6 X 10(-9)M. Calculated in terms of somatostatin binding per U 5'nucleotidase activity, the binding for plasma membranes becomes 8.4 X 10(-14) mole/U 5'nucleotidase; secretory vesicles 4.4 X 10(-13) mole/U 5'nucleotidase. Thus, secretory vesicles are fivefold richer in high affinity receptor sites than plasma membranes. It is suggested that in order for somatostatin to act, both a receptor and an effector unit must be present. In the case of tissues secreting polypeptide hormones by granule extrusion, the secretory vesicle may possess both the receptor and the effector units. It is postulated that during the process of fusion of the plasma and secretory vesicle membranes, a high affinity binding site for somatostatin is incorporated into the plasma membrane, thereby allowing somatostatin to act at a specific locus in the cell in inhibiting hormone release.
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PMID:The relationship between somatostatin binding and cyclic AMP-stimulated protein kinase inhibition. 610 15