Diabetes and insulin: actions and interactions upon the glucose metabolism of rat aorta.

We studied the glucose oxidation to CO2 and the incorporation of glucose into lipids by thoracic aorta from streptozotocin-diabetic rats in two circumstances: 9 minutes exposure of the isolated aorta to insulin, perfused in situ; and one-week treatment with either low--4 units (U)--or high--12 U--daily doses of insulin. Diabetes inhibited the glucose metabolism of media and adventitia. Perfusion with insulin did not influence the depressed metabolism of media but increased that of adventitia. Four units insulin treatment normalized the synthesis of glucose-derived lipids by the media, whereas 12-U treatment brought it to levels significantly higher (+23%) than those found in nondiabetic rats. We conclude that: (a) a haemodynamic explanation cannot account for the in vitro insulin resistance of media found in diabetes; (b) insulin treatment exerts a dose-dependent lipogenic effect upon the media, which might favour an atherogenic role for therapeutic hyperinsulinaemia in insulin-dependent diabetics.