Atrial natriuretic peptide receptors and activation of guanylate cyclase in rat cardiac sarcolemma

Abstract

Two classes of atrial natriuretic peptide (ANP) receptors are present in purified sarcolemmal membrane fractions isolated from rat ventricle. Scatchard analysis using [ 125I]-ANP reveals high affinity (K d approximately 10 −11 M) and low affinity (K d approximately 10 −9 M) binding sites. Basal guanylate cyclase activities associated with these membrane fractions range from 3.2 ± 1.3 pmol/min/mg protein in the presence of Mg 2+ to 129 ± 17 pmol/min/mg protein in the presence of Mn 2+. Millimolar concentrations of adenosine triphosphate (ATP) potentiates Mg 2+- but not Mn 2+-supported activity. Binding of ANP to the low affinity site but not the high affinity site results in a maximum 2-fold activation of Mn 2+- and up to 6-fold activation of Mg 2+/ATP supported guanylate cyclase activities.