Insulin resistance and not hyperinsulinaemia determines erythrocyte Na+/Li+ countertransport in non-insulin-dependent diabetes mellitus.

Insulin resistance and increased erythrocyte Na+/Li+ countertransport activity are well documented in subjects with essential hypertension, raising the question whether compensatory hyperinsulinaemia might be responsible for activating Na+/Li+ countertransport. We measured Na+/Li+ countertransport in 63 non-nephropathic non-insulin-dependent diabetic subjects (36 hypertensive, 27 normotensive), finding no correlation with fasting levels of insulin (r = 0.074, P = 0.28), despite using a sensitive and specific insulin assay. In contrast, in 33 of the subjects in whom insulin sensitivity was measured, Na+/Li+ countertransport correlated significantly with the whole body glucose clearance rate (r = -0.37, P = 0.036). It is concluded that increased Na+/Li+ countertransport may be a cellular marker for insulin resistance, but that hyperinsulinaemia is not likely to be the factor which mediates this relation.