Description: We previously reported that chronic systemic treatment of rats with a nitric oxide synthase inhibitor leads to a selective decrease in renal medullary blood flow, retention of sodium, and the development of hypertension. In the present studies, we used protein blotting techniques to determine the whole tissue distribution and relative quantitation of the different nitric oxide synthase isoforms in the renal cortex and medulla of Sprague-Dawley rats maintained on a low (0.4% NaCl) or high (4.0% NaCl) dietary salt intake.