SYSTEMIC AND REGIONAL EFFECTS OF ENDOTHELIN IN RABBITS: EFFECTS OF ENDOTHELIN ANTIBODY

SUMMARY 1. The effects of porcine endothelin‐1 (10 ‐12 ‐5 × 10 ‐10 mol/kg) on arterial blood pressure (BP) and the renal, mesenteric and carotid blood flow (BF), and the effects of endothelin‐1 antibody were studied in rabbits. 2. Endothelin‐1 caused a sustained increase in BP. The renal, mesenteric and carotid BF were decreased dose‐dependently by endothelin‐1. The approximate half‐maximal effective values (ED 50 ) were 5.5 × 10 ‐11 , 8.6 × 10 ‐11 and 2.0 × 10 ‐10 mol/kg for renal, mesenteric and carotid BF respectively. Compared with carotid BF, the renal and mesenteric BF responses were significantly more sensitive to endothelin‐1. 3. Combined administration of endothelin‐1 and its antibody showed a significant inhibition of the BP and renal BF responses. However, endothelin‐1 antibody alone did not change either BP, renal BF, mesenteric BF or carotid BF in vivo. 4. The present results demonstrate that endothelin is a potent vasoconstrictor in vivo. However, circulating endothelin may not contribute to the control of BF and BP. The role of endothelin as a local modulator of the vascular tone remains to be investigated.