The effect of lysine acetylsalicylate on somatostatin inhibition of insulin secretion induced by arginine

The inhibitory effect of somatostatin (SRIF) on immunoreactive insulin release and on many other hormonal secretions has been widely studied in both animal and man. However, the mechanism by which SRIF acts on these functions remains poorly defined. Aim of this study is to determine the inhibitory effect of SRIF on insulin secretion induced by arginine after the administration of lysine acetylsalicylate (LAS) in a dose which inhibits the endogenous synthesis of prostaglandins. Ten healthy informed volunteer subjects were studied. Four studies were carried out in randomized order, each one separated by a three day interval. The first study was a test of arginine (25 g i.v. in 30 min). The second study was a test of arginine with SRIF infusion (150 micrograms bolus followed by 100 micrograms/h for 120 min). The third study was a test of arginine with an infusion of SRIF and LAS (66 mg/min for 120 min). The fourth study was a test of arginine with LAS infusion. Plasma insulin levels were determined by radioimmunoassay. After arginine administration the typical biphasic insulin response was observed with a precocious peak at 3 min and a late peak at 30 min. This response is not significantly modified under LAS infusion. With the infusion of SRIF at a dose of 100 micrograms/hr after arginine administration only a very modest insulin response was observed. The addition of LAS does not modify the inhibitory effect of SRIF on insulin secretion induced by arginine. This result demonstrates that the inhibitory action of SRIF on the secretion of insulin is not dependent upon the activation of the endocellular prostaglandin system.