Abstract
The effects of papaverine, benactyzine and D600 on Ca2+ efflux from the taenia coil of guinea pig into a Ca2+-free physiological solution were studied. The effluxed free Ca2+ concentrations in the solution were continuously monitored during 30 min by means of a Ca2+-selective electrode. Papaverine (5×10-5 and 10-4 M) increased the amount of effluxed Ca2+ after a 10-min efflux time. The increase in the rate of Ca2+ efflux by papaverine was observed after a 4-min efflux time and lasted for the following 15-20 min. Dibutyryl cyclic AMP induced the increase in Ca2+ efflux in a similar manner as papaverine. Benactyzine at a concentration of 10-4 M, which exerts a non-specific antispasmodic action, produced an increase in the amount of effluxed Ca2+ during a 30-min efflux period, and the increase in the rate of Ca2+ efflux was observed only 1 min after the efflux initiation. D600 (10-6M) had no effect on Ca2+ efflux and the rate of Ca2+ efflux, while an increase in the concentration of D600 to 10-5 M produced an enhancement of Ca2+ efflux and an increased rate of efflux, during the 30-min efflux period. These results suggest that smooth muscle relaxants, papaverine, benactyzine and D600, may increase Ca2+ efflux from the guinea pig taenia coli into a Ca2+ -free physiological solution, in a different manner(s).
