Increased vasodilatory prostaglandin production in the diabetic rat retinal vasculature

Purpose. This study was undertaken in order to investigate whether the production of vasodilatory prostaglandins is increased in the retinal vasculature of the diabetic rat. Methods. Diabetes was induced in male Sprague-Dawley rats using streptozotocin. Diabetic rats were left uncontrolled for 3-4 weeks or were treated with insulin replacement throughout the period of diabetes. Control rats were age-matched. Retinal vessels extracted from retinae removed at sacrifice were incubated in a physiological salts solution. Prostaglandin E and prostaglandin I-2 were measured in collected medium. Results. The production of both prostaglandin E and prostaglandin I-2 by blood vessels isolated from the retina was increased by approximately 40% in streptozotocin-diabetic rats, compared to controls, within 4 weeks of the onset of diabetes. This increase was reversed by treatment of streptozotocin-diabetic rats with insulin. The increase in prostaglandin production was not due to alteration in the maximal capacity of cyclooxygenase enzyme. Conclusions. Increased production of vasodilatory prostaglandins occurs in the rat retinal vasculature early in diabetes. Prostaglandins may contribute to altered retinal hemodynamics in early diabetic retinopathy.