Insulin secretion in the spiny mouse (Acomys cahirinus). Dose and time kinetic studies with glucose in vivo and in vitro.

Abstract

Plasma insulin responses to the intravenous injection of glucose in the doses of 0.5, 1.5, and 3.0 gm./kg. were compared in spiny mice (Acomys cahirinus) and weight-matched Swiss albino mice. The mean early (two-minute) plasma insulin response was significantly lower in Acomys at all doses of glucose injected; whereas, at later times (5, 15, and 30 minutes), differences in plasma insulin concentrations in the two species of mice were smaller or nonexistent. Plasma glucose clearance was significantly less in the Acomys. In terms of glucose dose kinetics, there was a decreased capacity of the mean plasma insulin response in Acomys compared with albino mice at two minutes; whereas, at later times, the mean dose response curve for Acomys was shifted to the right of that for albino mice, indicating a decreased sensitivity to glucose in the Acomys. There was, however, a large variation between the plasma insulin responses of the eight individual Acomys mice tested. There was a significant correlation in individual Acomys between the plasma insulin response, expressed as an insulinogenic index, integrated over the thirty minutes after injection of glucose 3.0 gm./kg. in vivo, and the insulin released from pancreatic islets obtained from the corresponding Acomys and perifused for thirty minutes with glucose 1,000 mg./100 ml. in vitro (r = 0.77, p less than 0.05). It is concluded that the rate and magnitude of the insulin response to glucose in an individual Acomys reflects mainly the degree of sensitivity to glucose of the pancreatic beta cells in that animal.