ADAPTIVE SUPERSENSITIVITY AND THE NA+ K+ PUMP IN THE GUINEA-PIG VAS-DEFERENS - TIME-COURSE OF THE DECLINE IN THE ALPHA-2 SUBUNIT/

Adaptive supersensitivity in the guinea pig vas deferens has been show n previously to be associated with decreases in transmembrane potentia l, Na+/K+-ATPase activity, [H-3]ouabain binding sites, and density of the alpha 2 subunit of the pump. One of several procedures that induce adaptive supersensitivity in the guinea pig vas deferens is neurotran smitter depletion by chronic administration of reserpine. Guinea pigs were treated with reserpine (1.0 mg/kg/day, intraperitoneally) for 2, 5, or 8 days. Tissues were homogenized and the concentration of the al pha 2 subunit was quantified by use of the selective antibody McB2, sl ot blot analysis, enhanced chemiluminescence, and densitometric analys is. As reported previously, the concentration of the alpha 2 protein w as reduced 41% after 5 days of pretreatment. The reduction was maintai ned at 8 days (37%). However, there was no change from control after 2 days of pretreatment with reserpine. Thus, the time course of the dec line in the alpha 2 subunit is similar to that of the appearance of su persensitivity, depolarization, and the declines in Na+/K+-ATPase and [H-3]ouabain binding established earlier. Based upon results in the li terature for several different tissues and species, membrane depolariz ation and decreases in Na+/K+ pump sites may represent widely occurrin g adaptive mechanisms.