Comparison of cylic and linear forms of somatostatin in the inhibiton of growth hormone, insulin and glucagon Secretion.

The relative potency of cyclic and linear somatostatin in their inhibitory action on GH, insulin and glucagon secretion was assessed in 7 normal adult men. Administration of linear or cyclic somatostatin as a single intravenous bolus (50 mug) resulted in a prompt and concomitant decline in both insulin and glucagon. While both peptides elicited a quantitatively similar suppression of glucagon secretion, the decline in basal insulin level was greater with the cyclic than with the linear preparation. Both the linear and cyclic form of somatostatin appears to be more potent in the inhibition of insulin than glucagon. No discernable change in plasma glucose and GH levels was observed.