Ca2+-dependent inhibition of smooth muscle adenylate cyclase activity

Michael T. Piascik, Bradford Addison, Michael Babich

Research output: Contribution to journalArticlepeer-review

9 Scopus citations


We have examined the inhibitory regulation by Ca2+ of the adenylate cyclase activity associated with microsomes isolated from bovine aorta smooth muscle. In the presence of 2 mm MgCl2, Ca2+ (0.8-100 μm) inhibited in a noncompetitive manner activation of the enzyme by GTP, Gpp[NH]p, or forskolin. In all instances the value for half-maximal inhibition was between 2 and 3 μm. In contrast, Ca2+ inhibited the activation by MgCl2 (2-50 mm), alone or in the presence of GTP, in a competitive manner. The inhibition of adenylate cyclase by 10 μm Ca2+ was reversed in the presence of either 5 or 25 μm calmodulin or troponin C. These data show that (i) Ca2+, at concentrations similar to those which activate smooth muscle contraction, inhibits the stimulation of adenylate cyclase by several activators; (ii) Ca2+ and Mg2+ compete for a common site on the smooth muscle adenylate cyclase complex; and (iii) the reversal of Ca2+-dependent inhibition by Ca2+-binding proteins may be produced by chelation of the metal by these proteins.

Original languageEnglish
Pages (from-to)28-35
Number of pages8
JournalArchives of Biochemistry and Biophysics
Issue number1
StatePublished - Aug 15 1985

Bibliographical note

Funding Information:
This work was supported in part by funds from the American Heart Association-Kentucky Affiliate. We thank Deborah Turner for the supervision the preparation of this manuscript and Susan Farmer for excellent technical assistance.

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology


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