Different contributions of endothelin-A and endothelin-B receptors in the pathogenesis of deoxycorticosterone acetate-salt-induced hypertension in rats

We investigated the involvement of actions mediated by endothelin-A (ETA) a nd endothelin-A (ETB) receptors in the pathogenesis of deoxycorticosterone acetate (DOCA)-salt-induced hypertension in rats. Two weeks after the start of DOCA-salt treatment, rats were given ABT-627 (10 [mg/kg]/d), a selectiv e ETA receptor antagonist; A-192621 (30 [mg/kg]/d), a selective ETB recepto r antagonist; or their vehicle for 2 weeks. Uninephrectomized rats without DOCA-salt treatment served as controls. Treatment with DOCA and salt for 2 weeks led to a mild but significant hypertension; in vehicle-treated DOCA-s aIt rats, systolic blood pressure increased markedly after 3 to 4 weeks. Da ily administration of ABT-627 for 2 weeks almost abolished any further incr eases in blood pressure, whereas A-192621 did not affect the development of DOCA-salt-induced hypertension. When the degree of vascular hypertrophy of the aorta was histochemically evaluated at 4 weeks, there were significant increases in wall thickness, wall area, and wall-to-lumen ratio in vehicle -treated DOCA-salt rats compared with uninephrectomized control rats. The d evelopment of vascular hypertrophy was markedly suppressed by ABT-627. In c ontrast, treatment with A-192621 significantly exaggerated these vascular c hanges. In vehicle-treated DOCA-salt rats, renal blood flow and creatinine clearance decreased, and urinary excretion of protein, blood urea nitrogen, fractional excretion of sodium, and urinary N-acetyl-beta-glucosaminidase activity increased. Such damage was overcome by treatment with ABT-627 but not with A-192621; indeed, the latter agent led to worsening of the renal d ysfunction. Histopathologic examination of the kidney in vehicle-treated DO CA-salt rats revealed tubular dilatation and atrophy as well as thickening of small arteries. Such damage was reduced in animals given ABT-627, wherea s more severe histopathologic changes were observed in A-192621-treated ani mals. These results strongly support the view that ETA receptor-mediated ac tion plays an important role in the pathogenesis of DOCA-salt-induced hyper tension. On the other hand, it seems likely that the ETB receptor-mediated action protects against vascular and renal injuries in this model of hypert ension. A selective ETA receptor antagonist is likely to be useful for trea tment of subjects with mineralocorticoid-dependent hypertension; whereas ET B-selective antagonism alone is detrimental to such cases.