Glucose transporters are developmentally regulated. GLUT1 is predominant in the fetus and newborn. GLUT2 in liver and GLUT4 in muscle and fatty tissue are predominant in the adult. GLUT1 is not insulin-regulatable and GLUT4 is insulin regulatable. Therefore, we hypothesize newborn rats could have a different response to insulin than the adult rat. Materials and Methods Ten day old and adult Sprague-Dawley rats were used after a 4 hour fast and an overnight fast, respectively. Radioactive 2DG with/without 10 unit/kg insulin (INS) was injected by cardiac puncture under pentobarbital anesthesia to evaluate glucose disappearance. 2DG was used because 2DG is not metabolized after phospholyration. Blood was serially collected by cardiac puncture at 0, 5,10,15,30 and 45 minutes after the injection. Plasma glucose(PG) concentration and radioactive 2DG concentration were measured by a oxidase method and scintilation counter, respectively. Glucose disappearance was calculated from plasma glucose concentration. Values for PG and 2DG were calculated as percent of initial values of PF and 2DG at 0 minute, respectively. Results PG and 2DG (%) at 45 minutes are in the Table.

Table 1
Full size table

Conclusion Young rats have decreased glucose disappearance in response to insulin when compared to adult rats, which appears to be developmentally regulated.