Ionic transport through model membranes. III. Contrasting effects of testosterone and 5-α-dihydrotestosterone. Dependence on temperature and bound water

Abstract

1. 1 The transfer of the dyestuff probe, methyl orange, from an aqueous phase into phospholipid-cholesterol micelles in an adjacent organic phase was found to be affected by testosterone quite differently than by dihydrotestosterone. The kinetics of transport of the probe proved extremely dependent in the presence of dihydrotestosterone upon the extent of prehydration of the organic phase. Rates were measured at controlled temperatures from 19 to 45 °C. 2. 2 For the system, lecithin-cholesterol-testosterone at selected concentrations, high rates of transfer of methyl orange were observed between 23 and 35 °C. Below 22 and above 36 °C, the transport rates were reduced to those observed with lecithin alone. 3. 3 For the corresponding system containing dihydrotostesterone the transition at 35 °C was essentially the reverse of that for the system containing testosterone. Low rates were observed below 35 °C, elevated rates above this temperature.