The action of the ionophore ionomycin in guinea-pig intestinal smooth muscle.
The ionophore ionomycin produced concentration-dependent (5 X 10(-9) to 5 X 10(-6) M) contractions in guinea-pig ileal longitudinal smooth muscle. Responses were dependent on extracellular Ca2+, consistent with the known role of this Ca2+ source in supporting excitation-contraction coupling to a variety of stimulants in this tissue. Responses were insensitive to atropine (10(-6) M) but were dependent upon extracellular Na+ and were completely blocked by low concentrations of the Ca2+-channel antagonists nicardipine, YC-93 (5 X 10(-7) M), and D-600 (5 X 10(-6) M). The behaviour of ionomycin is very similar to that shown by A 23187 in this tissue. Ionomycin, like A 23187, can apparently activate D-600 sensitive Ca2+ channels in the guinea-pig intestinal smooth muscle rather than simply translocating Ca2+EXT.
D000818:Animals; D002104:Cadmium / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology; D004987:Ethers / Q000494:pharmacology; D005711:Gallopamil / Q000494:pharmacology; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects*; D015759:Ionomycin; D008345:Manganese / Q000494:pharmacology; D009130:Muscle, Smooth / Q000187:drug effects*; D009529:Nicardipine; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology
D004987:Ethers; D002104:Cadmium; D005711:Gallopamil; D008345:Manganese; D015759:Ionomycin; D012964:Sodium; D009529:Nicardipine; D009543:Nifedipine; D002118:Calcium