The effects of Ca antagonists, manganese and lanthanum on cooling-induced contracture of depolarized vas deferens.
Lowering of temperature applied during the course of the tonic contraction of high-K-induced contracture of guinea-pig vas deferens induced an increase in tension which was sensitive to extracellular Ca. Verapamil and nifedipine inhibited the tonic contraction and cooling-induced tension development. Mn2+ and La3+ also showed inhibiting actions on the tonic contraction, which, however, was followed by slow re-elevation of the tension. Cooling treatment caused relaxation in the presence of either ion, which increased with repetition of the cooling treatment. By rewarming the preparation, a phasic contraction, which increased in height with repetition of the treatment, was observed. These effects in the presence of Mn2+ or La3+ were also observed in the absence of Ca or in preparations treated with caffeine in Ca-free solution (Ca-deprived preparation). Verapamil was capable of depressing these effects of Mn2+ and La3+. These results suggest the involvement of influxed Ca in the initiation of tension development by cooling. The decrease of extrusion through the cell membrane and/or uptake by intracellular binding sites at low temperature may be the cause of the cooling-induced tension development. Mn2+ or La3+ induces the tension development by their direct actions on contractile proteins which are differently affected by the changes in temperature.
D000818:Animals; D002118:Calcium / Q000502:physiology*; D003080:Cold Temperature; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007811:Lanthanum / Q000494:pharmacology*; D008297:Male; D008345:Manganese / Q000494:pharmacology*; D009119:Muscle Contraction; D009130:Muscle, Smooth / Q000502:physiology*; D009543:Nifedipine / Q000494:pharmacology; D014649:Vas Deferens / Q000502:physiology; D014700:Verapamil / Q000494:pharmacology
D008345:Manganese; D007811:Lanthanum; D014700:Verapamil; D009543:Nifedipine; D002118:Calcium