Effects of pinacidil on contractile proteins in high K⁺‐treated intact, and in β‐escin‐treated skinned smooth muscle of the rabbit mesenteric artery

Abstract

1 The effects of pinacidil were investigated on changes in cellular Ca2+ concentration ([Ca2+]i) and tension in intact and chemically skinned smooth muscle strips of the rabbit mesenteric artery.2 High K+ (128mM) produced a large phasic followed by a tonic increase in [Ca2+]

Effects of calyculin A on tension and myosin phosphorylation in skinned smooth muscle of the rabbit mesenteric artery

“…Chemically skinned smooth muscle strips were prepared by use of P-escin (Itoh et al, 1991). In preliminary experiments, 25 tLM P-escin was applied in an activating solution containing 10 gM Ca2+.…”

Membrane hyperpolarization inhibits agonist‐induced synthesis of inositol 1,4,5‐trisphosphate in rabbit mesenteric artery.

“…It was recently reported that in oc-toxintreated skinned smooth muscle strips of the rabbit mesenteric artery, a high concentration of pinacidil (100 ,tM) inhibited Ca2+-induced contraction in the presence but not in the absence of NA (Anabuki, Hori, Ozaki, Kato & Karaki, 1990). In ,-escin-treated skinned smooth muscle of the rabbit mesenteric artery, although pinacidil (10 /LM) inhibited the Ca2+-induced contraction in the presence or absence of NA (Itoh, Suzuki & Kuriyama, 1991), pinacidil (> 3 ,SM) inhibited Ca2+-induced contraction more in the presence of NA with GTP than in the absence of NA and GTP. These results suggest that a high concentration of pinacidil may directly inhibit the NA-activated hydrolysis of phosphatidylinositol-4,5-bisphosphate without its corresponding membrane hyperpolarizing action.…”

Characteristic features of noradrenaline‐induced Ca2+ mobilization and tension in arterial smooth muscle of the rabbit.

“…Subsequently, it was found that, in skinned vascular smooth muscle strips treated with a-toxin, phenylephrine enhanced the Ca2+ sensitivity of the contractile proteins (Nishimura, Kolber & van Breemen, 1988;Kitazawa, Kobayashi, Horiuti, Somlyo & Somlyo, 1989). Moreover, we recently reported that NAd with GTP enhanced the amplitude of contraction induced by 0 3 AM Ca2+ in /-escintreated skinned smooth muscle strips of the rabbit mesenteric artery (Itoh, Suzuki & Kuriyama, 1991 To enable simultaneous recording of isometric tension and [Ca2+]i, fine circularly cut strips (0 3-0X5 mm length, 004-0 05 mm width, 0 02-0 03 mm thickness) were prepared as previously described (Itoh et al 1983). Endothelial cells were removed by gentle rubbing of the internal surface of the vessels using small knives.…”

“…Experiments on chemically skinned smooth muscle Chemically skinned smooth muscle strips were made using /1-escin . The methods used to make skinned muscles and the composition of the solution have been described elsewhere Kobayashi et al 1989;Itoh et al 1991 For experiments on skinned muscle, the composition of the relaxing solution was: 87 mm potassium methanesulphonate (KMS), 20 mm piperazine-N-N'-bis-(2-ethanesulphonic acid) (PIPES), 5-1 mM Mg(MS)2, 5-2 mm ATP, 10 mm phosphocreatine and 4 mm ethyleneglycol-bis-(/-aminoethylether)-N,V,N',N'-tetraacetic acid (EGTA). To enable measurement of Ca2' release from skinned strips, the concentration of EGTA was reduced to 50 /tm and 2 /M Fura-2 added (as described above).…”