IMMUNOREACTIVITY FOR NITRIC-OXIDE SYNTHASE AND ENDOTHELIN IN THE CORONARY AND BASILAR ARTERIES OF RENAL HYPERTENSIVE RATS

The ultrastructural localization of immunoreactivity to nitric oxide s ynthase (type-III and type-II) and endothelin-1 was examined by using pre-embedding peroxidase-antiperoxidase techniques in the coronary and cerebral basilar arteries in renal hypertensive rats, Renal hypertens ion was produced by excision of the right kidney and clipping of the l eft renal artery. Controls were normotensive sham-operated rats (right surgical nephrectomy; a clip inserted near the left renal artery). Bo th in controls and hypertensive rats, immunore-activities for nitric o xide synthase-III and endothelin-1 were localized within subpopulation s of endothelial cells. In addition, signs of translocation of nitric oxide synthase-III were noted from the cytoplasm to the Golgi complex in endothelial cells of the basilar artery of hypertensive animals. Ne ither controls nor hypertensive rats showed immunoreactivity for nitri c oxide synthase-II. Preparations of the right coronary artery from hy pertensive rats displayed fewer endothelial cells positive to nitric o xide synthase-III than in controls, although there were no significant changes in the distribution of endothelin-1-positive endothelial cell s in the coronary artery of hypertensive rats. In contrast, the basila r artery from hypertensive rats displayed no changes in the percentage of endothelial cells immune-positive either for nitric oxide synthase -III or for endothelin-1. In consequence, the ratio of nitric oxide sy nthase-III:endothelin-1 was reduced in the coronary but not in the bas ilar artery-. Therefore, the nitric oxide/endothelin-1 system appears to play different roles in the coronary and cerebral circulations duri ng renal hypertension.