Growth hormone and insulin secretory responses to arginine in the sheep, pig, and cow

Abstract The intravenous infusion of l -arginine (0.5 gm/kg) resulted in a prompt and significant increase in plasma growth hormone (GH) in sheep and cows but not in pigs. The amino acid also elicited a marked increase in plasma insulin in sheep and cows, but the insulin secretory response of pigs, although statistically significant, was considerably less than that seen in the two ruminant species studies. The infusion of arginine over a 2-hour period elicited a sustained increase in both plasma GH and insulin in sheep. The insulin secretory system appeared to be more sensitive to the amino acid than the GH release mechanism, since an arginine infusion of 0.25 gm/kg elicited an insulin secretory response equal to but a GH response significantly smaller than that seen with 0.5 gm/kg. Comparable GH and insulin secretory responses were noted with arginine infusion repeated at 105-minute intervals. Hyperglycemia, produced by glucose infusion, decreased but did not completely block the GH response to arginine in sheep.