Ineffectiveness of protamine zinc somatostatin as a long-acting inhibitor of insulin and growth hormone secretion.
The present studies examined the duration of inhibitory action of a preparation of cyclic somatostatin (SRIF) in suspension with protamine zinc (PZ) on (1) physiologic growth hormone (GH) and immunoreactive insulin (IRI) secretion during feeding in the rat and (2) plasma IRI levels in a 10-year-old boy with idiopathic hyperinsulinemic hypoglycemia. Chronically cannulated adult male rats were administered 250 microgram PZ-SRIF subcutaneously twice daily at 12-h intervals for 7 days. Control animals received the PZ vehicle on the same schedule. On the test day, blood samples were obtained every 15 min for periods of 6 h following a single PZ-SRIF injection 1.5 h prior to sampling. Prominent GH secretory bursts were still evident in all PZ-SRIF-treated rats and these pulses occurred at the predictable time in relation to the light-dark cycle. Plasma IRI levels were typically elevated in response to feeding and no significant differences were observed in the mean 6-h GH, IRI, and glucose levels of PZ-SRIF-treated rats when compared with PZ-treated controls. In the boy with idiopathic hyperinsulinemic hypoglycemia, subcutaneous injection of 200 microgram PZ-SRIF depressed plasma IRI levels for only 30 min. These results suggest that PZ is not the agent of choice for significant prolongation of the inhibitory action of SRIF on IRI and GH secretion.
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D002648:Child; D004338:Drug Combinations / Q000008:administration & dosage; D013006:Growth Hormone / Q000378:metabolism*; D006801:Humans; D006946:Hyperinsulinism / Q000378:metabolism; D007328:Insulin / Q000378:metabolism*; D000078790:Insulin Secretion; D008297:Male; D011479:Protamines / Q000008:administration & dosage*; D051381:Rats; D013004:Somatostatin / Q000008:administration & dosage* / Q000494:pharmacology; D013997:Time Factors
D001786:Blood Glucose; D004338:Drug Combinations; D007328:Insulin; D011479:Protamines; C029997:somatostatin, protamine zinc-; D013004:Somatostatin; D013006:Growth Hormone