Effect of vitamin A deficiency on cardiovascular function in the rat

Abstract

Selected parameters of cardiovascular function were evaluated in vitamin A-deficient rats at 70 days of age. Resting heart rate was increased by an average of 100 bpm (21.4 ± 2.7%), whereas resting systolic blood pressure was normal in vitamin A-deficient animals. The maximal contractile force developed per milligram weight of tissue by aortic rings excised from vitamin A-deficient animals was reduced in response to high potassium (–25.0 ± 8.7%) and phorbol 12,13-dibutyrate (–36.8 ± 8.4%) but was only slightly reduced in response to norepinephrine (–17.8 ± 11.1%). Intimal rubbing to remove the endothelium had no effect on the loss in contractile responsiveness, and the relaxant response to acetylcholine was similar between control and vitamin A-deficient tissue groups. This suggests that the decrease in contractility of vascular smooth muscle from the vitamin A-deficient rats did not involve altered release of endothelium-derived vasoactive factors. Western blot analysis suggested a reduction in the protein levels of several differentiation markers including α-actin (–22%), calponin (–37%), desmin (–37%), and vinculin (–40%), whereas the level of PKCα was unchanged from control values. Our findings indicate a significant decrease in contractile responsiveness of aortic smooth muscle of the vitamin A-deficient rat that may be associated with a down regulation in the expression of contractile-related proteins.Key words: vitamin A, retinoids, in vivo, cardiovascular, contractility, blood pressure.