Forskolin as a probe of adenylate cyclase of adipocytes

Abstract

New information regarding the relationship between the agonist receptor and the regulatory and catalytic components of adenylate cyclase has been obtained by applying forskolin in combination with several different activators of adenylate cyclase. Adipocyte adenylate cyclase cannot be fully activated by forskolin; maximal stimulation by forskolin can be further enhanced by Gpp(NH)p. The effect of Gpp(NH)p on membrane enzyme differs between rat and rabbit and between enzymes of membrane-bound and solubilized preparations of rat adipocytes. Conditions that produce maximal activation of the membrane adenylate cyclase have been found. Gpp(NH)p and NaF are both activators of adenylate cyclase but mutually oppose each other. These findings indicate multiple activatable forms of catalytic components and multiple activatable forms of regulatory components of adenylate cyclase.