Ion content and ion fluxes in the smooth muscle cells of the longitudinal layer of the guinea-pig's vas deferens

Summary

The intracellular K⁺, Cl⁻ and Na⁺ concentrations in the vas deferens cells of the guinea-pig have been estimated from the total ion content, the sorbitol space and the dry wt/wet wt ratio. The exchange of K⁺, Cl⁻ and Na⁺ was studied by following the uptake and the efflux of these ions with radioactive isotopes. The following steady state flux values have been calculated;m _K, 2.8 p-moles x cm⁻² x sec⁻¹;m _Cl, 13.2 p-moles x cm⁻² x sec⁻¹ andm _Na, 7.4 p-moles x cm⁻² x sec⁻¹. The values for the permeability constants calculated by the constant field assumptions from the ion fluxes are forP _K 8.9×10⁻⁸ cm/sec;P _Cl 9.7×10⁻⁸ cm/sec and forP _Na 2.1×10⁻⁸ cm/sec. The introduction of these values and of the concentrations in the Goldman equation give a resting potential of −30 mV. This value is only half of the value of the measured resting potential. One of the possible explanations for the discrepancy between the measured resting potential and the calculated one is that the resting potential of these smooth muscle cells is partly a diffusion potential and partly due to the operation of an electrogenic sodium pump.