Effects of androgen on corpus cavernosum : role of the plasma membrane calcium pumps /

Abstract

This study was designed to investigate the relative importance of the intracellular and extracellular calcium stores in mediating the contraction and relaxation of corporal cavemosal smooth muscle (CCSM) tissues. This study also investigated the effects of androgens on the calcium pump mechanism(s) responsible for the relaxation of this tissue. To determine the relative importance of the intracellular and extracellular calcium stores in CCSM relaxation, isolated CCSM tissues were treated with cyclopanazoic acid (CPA) or DMSO (control) before being contracted by norepinepherine (NE). Sodium nitroprusside (SNP) was then added to the tissues to induce relaxation. Finally, percent relaxations were recorded for each group. The effects of androgens on the calcium pump mechanism(s) responsible for CCSM relaxation were studied by dividing rats into intact, castrate, and testosterone replacement treatment groups. Isolated CCSM tissues were placed in calcium free media and treated with CPA. Next, CCSM contractions were induced by the addition ofNE and CaCh to the media. SNP was then added to the media to induce relaxation. Again, percent relaxations were recorded for each group. Results from this study indicate that the most important mechanism responsible for the removal of cytosolic calcium from CCSM is located on the plasma membrane. This study also shows that castration significantly reduces the relaxation ofCCSM, presumably by affecting the plasma membrane mechanism(s) responsible for the removal of calcium from the cytosol. Testosterone replacement was able to restore CCSM relaxation to normal levels. These results indicate that the calcium regulating mechanism utilized by CCSM is, to some extent, androgen regulated.