The effect of L-type calcium channel modulators on the mobilization of intracellular calcium stores in guinea-pig intestinal smooth muscle

摘要

1 The action of Ca~(2+) channel modulators has been examined on the intracellular Ca~(2+) signal in the longitudinal smooth muscle cells of the guinea-pig intestine after exposure to histamine and to agents known to affect intracellular Ca~(2+) stores. Isometric contraction has been measured simultaneously with front-surface fluorometry of fura 2-loaded preparations. 2 Histamine (10 μM) evoked a phasic and tonic increase in [Ca~(2+)]_i and contraction which were both sensitive to the Ca~(2+) channel blockers, nimodipine and D600. 3 Caffeine (10 mM) evoked in rapid increase in [Ca~(2+)]_i which was sustained as long as the preparation was exposed to the drug, whereas the contractile response was only phasic. In the presence of nimodipine 1 μM, the phasic contraction was absent although the fura 2-Ca~(2+) signal amounted to 32% of the control.