The role of plasma membrane calcium pumps in regulating relaxation of rat corpus cavernosum smooth muscle in vitro /

Abstract

These experiments were designed to investigate the roles of the plasma membrane Ca2+pumps in regulating relaxation of CCSM tissue in vitro. To distinguish the significant importance of these two plasma membrane pumps in determining CCSM relaxation, two different experiments were performed. The first experiment compared the relaxation of isolated CCSM tissues in Kreb's (control) versus Na+ -reduced solution. The isolated CCSM tissue was treated with norepinephrine (NE) to stimulate contraction, and sodium nitroprusside (SNP) to induce relaxation. Percent relaxation values were then recorded for each group. This experiment focused on the Na+1 Ca2+exchanger and its effects on relaxation of the CCSM. The second experiment compared isolated CCSM tissue in three different groups of media; Kreb's (control) wi DMSO, carboxyeosin wi DMSO, and Na+-reduced solution wi carboxyeosin. The drug carboxyeosin is believed to be an inhibitor of the calmodulin-dependant Ca2+ATPase pump. Again, the isolated CCSM tissue was treated with NE to initiate contraction, carboxyeosin was then added to the media, and finally SNP was given for the CCSM tissue to undergo relaxation. This experiment examined the effects of inhibiting the calmodulin-dependant Ca2+ATPase pump on the relaxation of CCSM. Our results demonstrated that both the Na+ICa2+exchange pump and the calmodulin-dependant Ca2+ATPase pump play an important role in mediating relaxation of the CCSM tissue tested with the NO donor, SNP.