CALMODULIN ACTIVATES ADENYLATE-CYCLASE FROM RAT ANTERIOR-PITUITARY

  • 1 December 1987
    • journal article
    • research article
    • Vol. 32  (6) , 743-748
Abstract
Bovine brain calmodulin activated adenlyate cyclase in calmodulin-deficient rat anterior pituitary membranes. This activation appeared to be specific by the following criteria: calmodulin activation was Ca2+ dependent and responded biphasically to calcium displaying activation at low and inhibition at higher concentrations; calmidazolium, a potent calmodulin antagonist, inhibited calmodulin activation of adenylate cyclase; activation of the enzyme occurred in a dose-dependent manner, at calmodulin concentrations normally found in most cells (1- to 20-.mu.M range). However, this response was not saturated using calmodulin concentrations as high as 50 .mu.M. The data suggest that endogenous calmodulin can be dissociated from normal anterior pituitary adenylate cyclase, that the enzyme can be subsequently stimulated by addition of micromolar concentrations of calmodulin, and that this enzyme appears to be at least 50-fold less sensitive to calmodulin than is the brain adenylate cyclase.