Differential alterations of the circulating prosomatostatin-derived peptides during insulin-induced hypoglycemia in man.
Insulin-induced hypoglycemia stimulates a rise of somatostatin-like immunoreactivity (SLI) in the venous circulation of man. Plasma SLI is comprised of a heterogenous group of peptides including somatostatin-28 (SS-28) somatostatin-28-(15-28), somatostatin-28-(16-28), and prosomatostatin (Pro-SS). To determine which of these Pro-SS related peptides is released after hypoglycemia, we developed an immunoadsorption method that rapidly and accurately separates SS-28 from the other somatostatins. This method involves the selective retention of SS-28 on a conjugate of agarose with immunoglobulins that recognize an epitope in the NH2-terminal region of SS-28. Pro-SS, SS-28-(15-28), SS-28-(16-28), henceforth referred to collectively as SS-28-(15-28), and SS-28, once separated, were then analyzed by RIA with a COOH-terminal antibody. Ten normal men were studied after an overnight fast. Pork insulin (0.05 U/kg) was injected iv, and blood was collected before and after the onset of hypoglycemia. The mean basal SS-28-(15-28) level was 13 +/- 1 (+/- SEM) pg/mL, and the mean basal SS-28 levels were 19 +/- 3 (+/- SEM) pg/mL. Plasma SS-28-(15-28) did not increase after insulin administration, but the mean SS-28 level increased by 76% (P less than 0.01). We propose that the release of SS-28, presumably from the gastrointestinal tract, during hypoglycemia occurs as a result of activation of the autonomic nervous system and speculate that SS-28, because of its ability to inhibit insulin secretion, may be important in counterregulation during glucopenia.
D000328:Adult; D006801:Humans; D007003:Hypoglycemia / Q000097:blood* / Q000139:chemically induced; D007328:Insulin; D008297:Male; D010455:Peptides / Q000097:blood*; D011498:Protein Precursors / Q000378:metabolism*; D013004:Somatostatin / Q000097:blood* / Q000378:metabolism*; D053561:Somatostatin-28
D007328:Insulin; D010455:Peptides; D011498:Protein Precursors; D013004:Somatostatin; C028456:prosomatostatin; D053561:Somatostatin-28