STIMULATION OF RAT PLATELET ADENYLATE-CYCLASE BY AN ENDOGENOUS CALCIUM-DEPENDENT PROTEASE-LIKE ACTIVITY

  • 1 January 1982
    • journal article
    • research article
    • Vol. 8  (2) , 103-118
Abstract
The stimulation of adenylate cyclase by various exogenous proteases was described in several tissues. A 2- to 7-fold increase of adenylate cyclase activity in a particulate preparation from rat platelets following prior exposure of the homogenate to Ca is described. Calmodulin alone was unable to increase the adenylate cyclase activity and trifluoperazine only partially inhibited the Ca-dependent activation. Ca had a slight stimulatory effect on the particulate preparation but this activation was greatly enhanced by the addition of supernatant. Only the combined addition of Ca, supernatant and calmodulin to washed particulate preparations reconstituted the activation seen in homogenates. The activation was significantly inhibited by leupeptin and thiol reagents. Platelets contain a Ca-dependent protease-like activity that is able to increase adenylate cyclase activity in membrane fractions. This phenomenon may be involved in the regulation of adenylate cyclase activity in platelets.