Reduced transcoronary exchange and prostaglandin synthesis in diabetic rat heart

In perfused hearts of streptozotocin-diabetic rats the kinetics of a fluoresce indicator transit was measured after pulse injection of FITC-dextran 3. The fluorescence changes on the left ventricle could be described by two pseudo first-order processes with half times in the range of seconds (t/2) corresponding to the intravascular washout and a slow process (T/2) corresponding to the exchange between the extra- and the intravascular space. In diabetes both half times became prolonged, and the amount of FITC-dextran 3 exchanged between the two compartments was reduced, indicating an impaired transcoronary transport in diabetic hearts. There was a time-dependent reduction in the basal release of prostacyclin in hearts of control and diabetic rats. However, studied hearts of diabetic rats released less 6-keto-prostaglandin F1 alpha (PGF1 alpha) than controls. This impaired release of 6-oxo-PGF1 alpha could be prevented partly by adrenalectomy. Because diabetic hearts release more 6-oxo-PGF1 alpha than controls after application of arachidonic acid, these data suggest that the supply of arachidonic acid for the synthesis of prostaglandins is impaired in diabetes, but not the cyclooxygenase pathway itself. The reduced transcoronary transport and the impaired synthesis of prostacyclin might be early steps in the development of microangiopathic myocardial alterations in diabetes.