ACTH_1-24 Stimulates Muscle Cell Glucose Uptake

Summary

³H-2-deoxyglucose (2-DG) uptake was measured in L6A-1 rat skeletal muscle cells (a rapidly fusing subclone of L6), following addition of several concentrations (10^-16 to 10^-9M) of the N-terminal fragment of ACTH_1-24 to cells deprived of serum and insulin for 21 hours, but maintained in the presence of (5 μg/ml) insulin (stimulated state). There was a marked dose-dependent increase of 2-DG uptake at the various ACTH_1-24 (P < 0.001). There was no correlation between the time of exposure of the cells to serum-free conditions and the rate of uptake of 2-DG at the various ACTH_1-24 Concentrations both in the basal and insulin-stimulated states. Addition of catochalasin B (50 μM) to the cells, which inhibited both basal and insulin-stimulated uptake of 2-DG (by 70% and 91%, respectively) completely eliminated the enhancement of both of these uptake rates to 10^-12 MACTH _1-24 The results suggest that: 1) ACTH_1-24 stimulates carrier-mediated uptake of glucose in skeletal muscle cells. 2) The site of action of ACTH_1-24 is on the non-insulin mediated glucose uptake (NIMGU) system. 3) ACTH_1-24 may be a useful probe to delineate some of the events associated with the NIMGU pathway.

Key words

Glucose Uptake - ACTH - Muscle Cells