Red cell sorbitol: an indicator of diabetic control.

Intact human erythrocytes accumulate intracellular sorbitol in response to the medium's glucose concentration during in vitro incubations. Sorbitol was identified and measured both enzymatically and by gas-liquid chromatography. The sorbitol produced is most likely a result of the activity of aldose reductase, since (1) a low glucose concentration in the medium elicits this response, and (2) this activity is completely blocked by tetramethylene glutaric acid, a specific inhibitor of aldose reductase. Erythrocyte sorbitol levels in insulin-dependent diabetics are clearly above those of nondiabetics after an 8 h fast. A good correlation exists between red cell sorbitol content and coincident plasma glucose concentrations. Individual exceptions to this rule exist, however, and suggest that red cell sorbitol levels may provide information about in vivo polyol pathway activity that may be important in the pathogenesis of diabetes-associated complications.