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Mechanisms of vasoconstriction induced by endothelin‐1 in smooth muscle of rabbit mesenteric artery.
Author(s) -
Yoshida M,
Suzuki A,
Itoh T
Publication year - 1994
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1994.sp020188
Subject(s) - myosin light chain kinase , protein kinase c , chemistry , vasoconstriction , contraction (grammar) , medicine , endocrinology , ionomycin , phosphorylation , endothelins , endothelin receptor , endothelin 1 , receptor , biophysics , calcium , biology , biochemistry
1. The mechanism underlying the vasoconstriction induced by endothelin‐1 (ET‐1) was investigated by measuring the intracellular concentration of Ca2+ ([Ca2+]i), isometric force and phosphorylation of the myosin light chain (MLC) in endothelium‐denuded unskinned and beta‐escin‐treated skinned smooth muscle from resistance vessels of the rabbit mesentery. The role of protein kinase C (PKC) in the action of ET‐1 was studied in skinned smooth muscle using a synthetic peptide, PKC19‐36, which corresponds to the autoinhibitory domain of PKC. 2. ET‐1 (> 0.1 nM) induced slowly developing, maintained increases in [Ca2+]i and force. Nicardipine completely blocked the ET‐1‐induced increase in [Ca2+]i. BQ‐123 (an inhibitor of the ETA receptor) blocked the ET‐1‐induced contraction but IRL 1620 (Suc‐[Glu9,Ala11,15]‐ET‐1(8‐21), an agonist of the ETB receptor) failed to induce contraction. 3. In ionomycin‐ and 70 mM K(+)‐treated strips, ET‐1 shifted the [Ca2+]i‐force relationship to the left and enhanced the maximum amplitude of contraction induced by 2.6 mM Ca2+. In skinned smooth muscle treated with ionomycin, Ca2+ (0.1‐3 microM) increased both force and MLC phosphorylation, in a concentration‐dependent manner. ET‐1 with GTP shifted both the Ca(2+)‐force and Ca(2+)‐MLC phosphorylation relationships to the left without significant changes in the maximum responses. ET‐1 with GTP did not change the relationship between force and MLC phosphorylation. Similar effects were observed with phorbol 12,13‐dibutyrate (PDBu, an activator of PKC). These results indicate that the sensitivity of MLC phosphorylation to Ca2+ is enhanced both by ET‐1 with GTP and by PDBu. 4. PKC19‐36 (an inhibitor of PKC) modified neither the contraction nor MLC phosphorylation induced by 0.3 microM Ca2+ but blocked the PDBu‐induced enhancement of both these Ca(2+)‐induced responses. However, PKC19‐36 only partly inhibited the enhancement produced by ET‐1 with GTP on the Ca(2+)‐induced responses. PKC19‐36 did not modify the relationship between force and MLC phosphorylation in the presence either of ET‐1 with GTP or of PDBu. By contrast, BQ‐123, neomycin and guanosine 5'‐O‐(2‐thiodiphosphate) (GDP beta S) each abolished the ET‐1‐induced enhancement of the contraction induced by 0.3 microM Ca2+. 5. These results suggest that ET‐1 acts on the ETA receptor and increases Ca2+ influxes through an activation of the dihydropyridine‐sensitive Ca2+ channel, causing a long‐lasting and maintained contraction in resistance vessels of the rabbit mesentery.(ABSTRACT TRUNCATED AT 400 WORDS)