INCREASED ENDOTHELIN-1 CONTENT IN BLOOD-VESSELS OF DEOXYCORTICOSTERONE ACETATE SALT HYPERTENSIVE BUT NOT IN SPONTANEOUSLY HYPERTENSIVE RATS

Endothelin-1 (ET-1) is a powerful vasoconstrictor peptide produced in the endothelium of blood vessels that may play an important role in the control of local blood How and could be involved in the pathogenesis of hypertension. We investigated immunoreactive ET-1 (ir-ET-1) levels in acid extracts from blood vessels of deoxycorticosterone acetate (DOCA)-salt and spontaneously hypertensive rats. We found that segments of thoracic aorta and the mesenteric vascular bed contain significantly more ir-ET-1 (11.84+/-0.84 and 17.30+/-1.89 fmol, respectively) than uninephrectomized control rats (1.78+/-0.20 and 9.19+/-0.63 fmol, respectively; p<0.001). High performance liquid chromatography showed that ir-ET-1 of blood vessels of DOCA-salt hypertensive rats eluted in the same position as synthetic ET-1. Significantly increased ir-ET-1 was localized by immunohistochemistry in endothelial cells of aorta and large and small mesenteric arteries of DOCA-salt hypertensive rats. In contrast to the latter, in spontaneously hypertensive rats, vascular content of ir-ET-1 was similar to that of blood vessels of Wistar-Kyoto control rats, at both 6 and 16 weeks of age. High levels of vascular ET-1 may explain the downregulation of vascular endothelin receptors previously described in DOCA-salt hypertensive rats. Furthermore, this suggests that ET-1 may be involved in the maintenance of high blood pressure in mineralocorticoid hypertension.