Regulation of the alpha-adrenergic system in rat vas deferens

Regulation of the supersensitivity and subsensitivity of the alpha adrenergic (alpha-Ad) system of rat vas deferens cultured under various experimental conditions was investigated. Muscles cultured for 3 days in normal medium (Eagle's MEM) exhibited marked increase in maximal contraction to noradrenaline (NA) and high K+ (154 mM), while muscles cultured with NA (100 microM) were subsensitive to the stimulants. Studies on the binding of 3H-WB4101, an alpha-Ad antagonist, to the homogenates of normal, supersensitive and subsensitive muscles revealed that the changes in NA-sensitivity were not accompanied by changes in the number or affinity of alpha-Ad receptors in the muscles. The effect of NA in decreasing NA-sensitivity was depressed by an inhibitor of protein synthesis, puromycin or cycloheximide. These results suggest that NA may be important in regulation of the contraction, at least in part through protein synthesis, without affecting the number or affinity of alpha-Ad receptors.