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PP.27.07: PREHYPERTENSIVE ALTERATIONS OF ARTERIAL AND VENOUS REACTIVITY IN A RAT POLYCYSTIC OVARY SYNDROME MODEL. EFFECTS OF PARALLEL VITAMIN D3 ADMINISTRATION

Objective: Polycystic ovary syndrome (PCOS) affects 4–10% of fertile women. It is already known that insulin resistance, altered metabolic status and hypertension occur in these patients. Our aims were to clarify the effects of dihydrotestosterone(DHT)-induced PCOS on carbohydrate metabolism, arteriovenous biomechanics, pharmacological reactivity and insulin-induced arterial vasorelaxation in a rat model and the possible modulatory role of vitamin D3 (VitD). Design and method: Female rats were subjected to chronic DHT treatment (83 &mgr;g/100 g/day). Some of them obtained vitD treatment (120ng/100 g). Oral glucose tolerance test (OGTT) with insulin level measurements was performed. After ten weeks, arterial and venous contractility and relaxation were tested in gracilis arterioles and saphenous veins by pressure arteriography. The insulin induced dilation of the arteries was also tested. Results: Blood glucose level was normal in all animals, however, this was accompanied by significantly higher 120’ insulin levels in DHT treated rats. Insulin elevation was prevented by concomitant vitD treatment. DHT treatment increased the morphological diameter, wall stress and distensibility of resistance arterioles, reduced their ability to contract in response to norepinephrine (NE, p < 0.05), reduced acetylcholine- (ACh) and insulin-induced vasodilation (p < 0.01). Increased diameter, wall thickness, and distensibility as well as decreased vasoconstriction of the saphenous veins were detected after the DHT treatment. Concomitant vitD treatment lowered the mechanical load of the arterioles and veins, increased the contractile response and resulted in more relaxed vessels. VitD treatment restored insulin relaxation (full recovery at 240 mU/ml). Conclusions: Increased insulin resistance of DHT treated animals associates with reduced ability of the arterioles to relax in response to insulin. The arteries and veins with more rigid, less flexible walls show reduced endothelium- and smooth muscle-dependent vasorelaxation and constriction with a loss of NO-dependent relaxation compared with controls. This situation caused by hyperandrogenic state is improved in vessels by chronic vitD treatment without affecting NO relaxation. Veins showed wall remodeling that can be interpreted as an early sign of a varicose pathology and altered vasorelaxant mechanisms. The observed alterations form an important prehypertensive pathway of vascular damage in PCOS and might explain the clinical effectiveness of vitD.