Abstract. The effect of insulin on basal pancreaticoduodenal output of SRIH was investigated in vivo and compared in normal and alloxan diabetic dogs. The experiments were performed on anesthetized dogs having a T-shaped catheter inserted into the pancreaticoduodenal vein just at the exit of the pancreas for blood sampling. In normal dogs, an insulin infusion (1 IU/kg for 20 min) or an iv insulin injection (0.2 IU/kg over 30 sec) produced, before any change in glycemia, an immediate reduction of the venous pancreaticoduodenal output of SRIH. Then pancreaticoduodenal output of SRIH rose close to starting values and decreased again when blood glucose level became very low. In alloxandiabetic dogs, insulin infusion (1 IU/kg for 20 min) also induced an immediate inhibitory effect on pancreaticoduodenal SRIH output; the effect was more transient and from 20 min, unlike in normal dogs, an increase in pancreaticoduodenal output of SRIH was observed. In conclusion, exogenous insulin induces an immediate reduction in pancreaticoduodenal SRIH secretion both in normal and diabetic dogs, independently of basal blood glucose level and before any change in glycemia. In contrast, the delayed effect is different: SRIH secretion is reduced in normal dogs, whereas it is enhanced in diabetic dogs.
G. Ribes, R. Gross, D. Chenon and M. M. Loubatières-Mariani
A. Zerbib, G. Ribes, R. Gross, R. Puech and M. M. Loubatières-Mariani
Insulin and pancreatic somatostatin secretions were studied after stimulation with an arginine infusion (5 mmol/1) in isolated perfused pancreata of adult streptozotocin-diabetic rats. In the presence of 2.8 mmol/l glucose, arginine clearly stimulated insulin and somatostatin secretions in diabetic rats, whereas it was ineffective in normal rats. Thus, not only the B-cells, but also the D-cells of the pancreas from streptozotocindiabetic rats are hypersensitive to arginine. The infusion of insulin (4 U/l) did not modify this hypersensitivity of the D-cells to arginine in pancreata of streptozotocindiabetic rats.