C-natriuretic peptide but not atrial natriuretic peptide increases cyclic GMP in cerebral arterial smooth muscle cells

A-type natriuretic peptide (ANP) is found primarily in the heart and is released into the circulation. C-type (CNP) is found principally in the brain and has also been detected in the systemic circulation. When injected, both peptides produce vasodilatation most likely by elevation of guanosine 3′5′- cyclic monophosphate (cGMP) in smooth muscle cells via two distinct receptors, NPR-A and NPR-B. In this present study, we determined the effects of these two peptides on intracellular cGMP in smooth muscle cells cultured from pig cerebral and peripheral arteries. In smooth muscle cells cultured from the left anterior descending coronary artery, ANP and CNP increased cGMP with equal potency and efficacy (EC₅₀ for ANP and CNP, 3.6 ± 0.2 × 10^-8 M and 6.7 ± 0.8 × 10^-8 M, respectively). In contrast, in smooth muscle cells from cerebral arteries, ANP was without effect while CNP increased cGMP in a concentration dependent manner ( EC₅₀: 9.6 ± 1.7 × 10^-8 M ). Stimulation of the soluble guanylyl cyclase with either nitroglycerin or nitroprusside was equivalent in the two cell types. The pattern of response of intracellular cGMP to CNP and ANP in isolated intact arteries from brain and heart was similar to that found in the cultured cells. These results suggest that smooth muscle cells in cerebral arteries express only NPR-B while cells from peripheral arteries can express both NPR-A and NPR-B.