Effect of hydralazine on myocardial plasma membrane fatty acid binding protein (PM-FABP) during diabetes mellitus.

Chronic treatment with the antihypertensive drug hydralazine did not affect the hyperglycemic state of streptozotocin (STZ)-diabetic rats but did prevent the serum hyperlipidemia that is synonymous with these diabetic animals. After 6 weeks, untreated STZ-diabetic rats exhibited a 659% increase in serum triglycerides and 292% increase in serum cholesterol versus age-matched non-diabetic rats. Hydralazine-treated STZ-diabetic rats had serum triglyceride and cholesterol levels that did not differ from controls. Myocytes from control rats showed a preference for binding of the unsaturated fatty acid analog cis-parinaric acid vs the saturated fatty acid analog trans-parinaric acid. This preference was not altered in STZ-diabetic rat myocytes; hydralazine-treatment of STZ-diabetic rats also showed no change in fatty acid preference. STZ-diabetes caused a decrease in the affinity (Kd) for the trans, but not the cis-parinaric acid. However, total binding of both analogs was increased in STZ-diabetes. Hydralazine treatment of STZ-diabetic rats resulted in even greater total binding of both analogs. Affinity for the trans analog was further decreased in these hydralazine-treated rats, but the affinity for the cis analog was increased beyond control animals. These results suggest that the diabetic state influences the binding characteristics of the myocardial PM-FABP and that hydralazine, while reducing serum lipids in diabetes, has complex effects on the fatty acid binding by this protein.