Effect of phosphatase inhibitors on estrogen receptors in the rat testis.

Testicular estrogen receptors were measured in the presence of phosphatase inhibitors, molybdate (MoO4=), wolframate (WO4=) and fluoride (F-), under different experimental conditions. At 0-4 degrees C, MoO4= was able to partially replace the stabilizing action of dithiothreitol (DTT) on cytosolic estrogen binding activity, suggesting a protective effect on reduced sulfhydryl groups. At 25 degrees C in the presence of DTT, the effect of MoO4= was observed in homogenates and low speed supernatants, being uneffective in cytosol. A possible mechanism of action through inhibition of phosphatase activity was supported by the use of WO4=. Acid phosphatase activity was inhibited in the presence of these agents, whereas alkaline phosphatase was unaffected. The addition of MoO4= also caused a significant inhibition of proteolytic activity. These results suggest that MoO4= would stabilize testicular estrogen binding activity through, at least, three mechanisms: 1) protection of reduced sulfhydryl groups; 2) inhibition of acid phosphatase, and 3) inhibition of proteolytic activity.