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

Abstract

SUMMARY1. Effects of noradrenaline (NAd) on changes in cellular Ca2+ concentration ([Ca21]i) and tension were investigated, and these effects were compared with those evoked by 128 mm K+ or caffeine in intact smooth muscle strips or by inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) or caffeine in ,-escin-treated chemically skinned smooth muscle strips of the rabbit mesenteric artery.2. In physiological solution containing 2-6 mm Ca2+, application of 128 mm K+ or 10 1UM NAd produced a phasic, followed by a tonic increase in [Ca2+]

Mechanisms of vasoconstriction induced by endothelin‐1 in smooth muscle of rabbit mesenteric artery.

“…Endothelial cells were removed by the gentle rubbing of the internal surface of the vessel using small knives. The absence of endothelial cells was confirmed by the inability of acetylcholine (1 /SM) to cause relaxation during contractions induced by noradrenaline (NA), as described previously (Itoh et al 1992). The strip was transferred into a chamber of 0-2 ml volume and mounted horizontally on an invert-microscope (Diaphoto TMD with special optics for epifluoresence; Nikon).…”

“…To enable loading of fura-2 into smooth muscle cells of the strip, 1/M acetoxymethyl ester of fura-2 (fura-2 AM) dissolved by dry dimethyl sulphoxide (1 mm stock solution) was applied for 1 h in Krebs solution at room temperature (20°C), as reported previously (Itoh et al 1992). Two alternative excitation wavelengths, 340 and 380 nm (each slit 5 nm) were applied by a spectrofluorimeter (Spex, Edison, NJ, USA) and the data analysed using customized software provided by Spex (DM-3000CM).…”

“…) Experiments on unskinned smooth muscle To enable the simultaneous recording of [Ca2+], and isometric force, fine circularly cut strips of the vessel (0 3-0 5 mm long, 0-04-0-05 mm wide, 0-02-0-03 mm thick) were prepared as previously described (Itoh et al 1992). Endothelial cells were removed by the gentle rubbing of the internal surface of the vessel using small knives.…”

“…Under these conditions, the background fluorescence intensity was 10-15 % of the fura-2 signals in smooth muscle strips at either excitation wavelength. Cytosolic Ca2+ concentrations were calculated using the formula described by Grynkiewicz, Poenie & Tsien (1985) and using in vitro calibration (Itoh et al 1992). …”

“…It was recently found that Ca2"-mobilizing agonists increase the sensitivity of contractile proteins to Ca21 through an activation of unidentified GTP-binding proteins in skinned smooth muscle (Kitazawa, Kobayashi, Horiuti, Somlyo & Somlyo, 1989;Itoh, Kajikuri & Kuriyama, 1992). ET-1, like other Ca2+-mobilizing agonists, increases the sensitivity of contractile proteins to Ca21 (Rembold, 1990;Nishimura, Moreland, Ahn, Kawase, Moreland & van Breemen, 1992).…”