Effects of cyclosporin A on blood pressure, baroreceptor reflex and renal function in dogs

The objective of this study is to investigate the effect of cyclosporin A (CsA) on baroreceptor reflex and renal function. Fifteen male mongrel dogs weighing 13-18 kg were divided into three groups and were treated orally as follows: group 1, enalapril 0.5 mg/kg per day for 10 days; group 2, CsA 20 mg/kg per day for 7 days; group 3, enalapril 0.5 mg/kg per day for 3 days combined with CsA 20 mg/kg per day for 7 more days. Measurements of blood pressure and of baroreflex response to sodium nitroprusside (SNP) and phenylephrine (PE) and renal function studies were performed on the days before and after receiving drugs. In group 1, both systolic arterial pressure (SAP) and mean arterial pressure (MAP) were unaltered, while diastolic arterial pressure (DAP) was reduced significantly. In group 2, all pressures (SAP, MAP and DAP) increased significantly. Group 3 showed no change in blood pressure. Studies of baroreceptor reflex showed that only dogs in group 2 had decreased sensitivity to PE without changing the setpoint. No change of the reflex was found in other groups. Renal function studies were unaltered in all groups. The data indicate that CsA increased blood pressure, which may be due to decreased baroreceptor reflex sensitivity mediated via activation of the renin-angiotensin-aldosterone system.