The effect of acetylsalicylic acid on insulin response to glucose and arginine in normal man

In 14 normal subjects, treatment with acetylsalicylic acid (ASA, 3.2 g daily for 3 days) a well known inhibitor of prostaglandin synthesis, caused a slight but significant decrease (p is less than 0.05) in basal plasma glucose levels; by contrast, basal insulin rose from 5 +/- 1 to 8 +/- 1 muU/ml (p is less than 0.01) after ASA. Pretreatment with ASA augmented the early insulin response to a standard IV glucose tolerance test (25 g) in 7 normal subjects (p is less than 0.05 at 2 min; p is less than 0.02 at 5 min; p is less than 0.01 at 10 min). No significant changes were detected in the rate of glucose utilization. 7 additional subjects received a standard arginine test without and with ASA pretreatment. Arginine stimulated insulin levels were increased after ASA (p is less than 0.01 at 15 min; p is less than 0.05 at 30 min; p is less than 0.05 at 45 min), whereas glucose values were lower than under basal conditions at all times, with significant differences at 105 (p is less than 0.02) and 120 (p is less than 0.05) min. A possible role of prostaglandins upon the insulin responses to glucose and arginine is discussed.

In vivo and in vitro experiments on relationships between PGA1 and glucose utilization

The in vivo and in vitro effects of PGA1 on glucose utilization were investigated in normal rats and in rats with alloxan-diabetes (50 mg/kg i.v. administered 48 hrs before experiment). The animals were divided into two groups. The first group -- which included both normal and diabetic animals -- was submitted to an IVGIT after a 12-h fast and during a sodium chloride infusion. In the second group -- which equally included normal and diabetic rats -- the same GTT was performed during a sodium chloride infusion in which PGA1 had been diluted, so that a dose of 0.5 g/kg/min was administered. This dose is devoid of any effect on cardiovascular activity. For in vitro experiments, glucose utilization was studied in the rat diaphragm incubated with insulin (200 muU/ml) and PGA1 (10 and 100 ng): results demonstrated that PGA1 enhances the insulin effect on glucose utilization and the enhancement is dose-dependent. The same results were observed also in the in vivo experiments: in normal rats PGA1 really improves glucose utilization without any interference with insulin secretion from B-cells. On the other hand, PGA1 has no effect on this utilization in diabetic rats. From our experiments it can therefore be concluded that PGA1 improves glucose utilization, showing a synergic action with the increased quantity of insulin secreted in response to a glucose load. No effect is noted when insulin secretion from B-cells is reduced or absent.