In situ hybridization shows increased endothelin-1 mRNA levels in endothelial cells of blood vessels of deoxycorticosterone acetate-salt hypertensive rats

Endothelin-1 is a potent vasoconstrictor peptide produced in blood vessels and other tissues that may play an important role in the control of local blood flow and could be involved in the pathogenesis of hypertension. Our previous studies have documented increases in endothelin-1 peptide content and gene expression in mesenteric arteries and thoracic aorta of deoxycorticosterone acetate (DOCA)-salt hypertensive rats. Although changes in endothelin-1 were observed in the blood vessels of hypertensive rats, the exact cellular sites of these changes were not identified clearly. In the present study we investigated endothelin-1 gene expression in DOCA-salt hypertensive rats by in situ hybridization histochemistry using a high specific activity 35S-labeled complementary RNA probe. Robust increases in endothelin-1 mRNA levels were observed in both mesenteric blood vessels and aorta of DOCA-salt hypertensive rats as compared with the vessels from the uninephrectomized control rats. In both cases it was shown clearly that these increased endothelin-1 mRNA levels only originated in the endothelial cell layer, not in the underlying smooth muscle cells. Higher expression levels of endothelin-1 mRNA by the endothelial cells of DOCA-salt hypertensive rats may play an important role in vascular hypertrophy and in the maintenance of elevated blood pressure in this and perhaps other models of experimental hypertension.