ABSTRACT
Pancreatic somatostatin (SRIF) secretion was examined using the RIA described in earlier paper. Ten isolated rat pancreatic islets were incubated for 30 min in 1 ml Krebs-Ringer bicarbonate buffer. Glucose (5.6 mM) caused a small but significant increase of SRIF secretion. The maximal secretion rate was observed at 16.7 mM glucose, and the half-maximal rate was seen at about 9.7 mM. Islets preincubated with 16.7 mM glucose released higher levels of SRIF and insulin during the subsequent incubation with 16.7 mM glucose than did islets preincubated with 2.8 mM glucose. Glucose-induced SRIF secretion was suppressed by epinephrine, but beta-adrenergic stimulation (epinephrine and phentolamine) produced an increase in SRIF secretion. Islets taken from rats 2 days after streptozotocin administration released minimal amounts of insulin. Basal and glucose-induced SRIF secretion from these islets, which had relatively unchanged SRIF contents and D cell numbers, equaled SRIF secretion from control rat islets. Islets taken from rats 6 weeks after streptozotocin administration, however, had increased SRIF content and D cell numbers, and they oversecreted SRIF. We conclude that pancreatic SRIF secretion can be induced by glucose and modulated by catecholamines and preexposure to high glucose, and the duration and severity of diabetes may be an important determinant of the changes in pancreatic D cell structure and function.
Subject(s)
Diabetes Mellitus, Experimental/physiopathology , Glucose/pharmacology , Islets of Langerhans/metabolism , Somatostatin/metabolism , Animals , Blood Glucose/metabolism , Dose-Response Relationship, Drug , Insulin/metabolism , Insulin Secretion , Islets of Langerhans/drug effects , Male , RatsABSTRACT
The effect of hypophysectomy and bovine growth hormone (GH) administration on somatostatin (SRIF) content as well as gastrin content in the rat stomach was investigated. SRIF content was determined by a specific radioimmunoassay. The total SRIF content in the stomach had decreased 4 weeks after hypophysectomy but was restored significantly in those rats which were subjected to bovine GH administration for 7 days after hypophysectomy. Furthermore, in control rats, an increase in SRIF content in the stomach was observed after 7 days of GH administration. Similar changes in total content of gastrin were observed after hypophysectomy and bovine GH administration, although these changes were not significant. These results indicate that GH may influence gastric function through changes in SRIF and gastrin content in the stomach.
