Antihypertensive effects of a mixed endothelin-A- and -B-receptor antagonist, J-104132, were augmented in the presence of an AT1-receptor antagonist, MK-954

The single oral administration of a mixed endothelin-A-and -B- (ET A /ET B ) receptor antagonist, J-104132 (L-753,037) decreased the blood pressure in conscious spontaneously hypertensive rats (SHR), stroke-prone SHR (SHRSP) and Dahl salt-sensitive hypertensive rats fed high-salt diet (DS-H) at doses of 3 and 10 mg/kg, with a duration of approximately 24 h. The magnitude of the antihypertensive effects was greater in DS-H than in SHR and SHRSP. Preproendothelin-1 mRNA expression in the kidney and aorta was greater (about twofold) in DS-H than that in normotensive Dahl salt-resistant rats fed high-salt diet (DR-H), while there was no difference in preproendothelin-1 mRNA expression between SHR and Wistar Kyoto rats (WKY). An ATI-receptor antagonist, MK-954 (Losartan), also attenuated hypertension in SHR and SHRSP at oral doses of 3 and 10 mg/kg, but had no effect in DS-H. The concomitant treatment with MK-954 and J-104132 showed additive antihypertensive effects in SHR and SHRSP. In DS-H, MK-954 potentiated the antihypertensive effects of J-104132. From these results, we suggest that: (1) the contribution of endothelin (ET) to the maintenance of hypertension is greater in salt-sensitive hypertensive models than in SHR and SHRSP; (2) the antihypertensive efficacy of ET A /ET B blockade is augmented by ATI-receptor blockade; (3) ET blockers alone or in combination with ATI antagonists could be useful in the treatment of hypertension for patients who do not respond adequately to renin-angiotensin system inhibitors alone.