Cardiovascular Response to Chronic Administration of C-type Natriuretic Peptide in Spontaneously Hypertensive Rats

Background: C-type natriuretic peptide (CNP) plays an important role in the regulation of cardiovascular function and morphology.We have previously demonstrated that CNP increases nitric oxide (NO) system activity in vivo in spontaneouslyhypertensive rats (SHR).Objective: The goal of this study is to evaluate the effect of chronic CNP administration on systolic blood pressure (SBP),cardiovascular function and the NO system in spontaneously hypertensive and normotensive rats.Methods: Twelve-week-old normotensive male Wistar rats and SHR were used. They received chronic infusion of saline orCNP (0.75 mg/h/rat) for 14 days via subcutaneously implanted osmotic pumps. Systolic blood pressure was measured and anelectrocardiogram and echocardiogram were performed. The left ventricle and the thoracic aorta were resected; nitric oxidesynthase (NOS) activity was determined using L-[U14C]-arginine and vascular reactivity was assessed.Results: Chronic administration of CNP decreased SBP in SHR. Cardiac output was lower in SHR and increased with CNP;however, CNP had no effect in normotensive rats. Spontaneously hypertensive rats had unbalanced aortic vasodilation andvasoconstriction responses, and CNP improved the vascular function. Nitric oxide synthase activity was greater in SHR andincreased with the 14-day CNP infusion, but this increase was lower than in normotensive rats.Conclusion: C-type natriuretic peptide induces cardiovascular and NO system changes which may be beneficial in this modelof hypertension.