Objective

To investigate the effect of cyclosporin A (CsA) on baroreceptor reflex and renal function.

Materials & Methods

Fifteen male mongrel dogs weighing 13-18 kg were divided into 3 groups and were treated orally as followed; group 1, 0.5 mg/kg/day enalapril (ENP) for 10 days; group 2, 20mg/kg/day CsA for 7 days; group 3, 0.5 mg/kg/day ENP for 3 days and combined with 20 mg/kg/day CsA for 7 more days. Blood pressure, baroreflex response to sodium nitroprusside (SNP) and phenylephrine (PE) and renal functions study were performed on the day before and after receiving drugs which represented the control and the post-treatment values, respectively.

Results

In group 1, both systolic arterial pressure (SAP) and mean arterial pressure (MAP) were unaltered while diastolic arterial pressure (DAP) were reduced significantly. Group 2 after received CsA, all pressure (SAP, MAP and DAP) increased significantly. Group 3 showed no change in blood pressure after drug treatments. Study baroreceptor reflex response to blood pressure changes showed that only group 2 dogs had decreased sensitivity to PE without changing setpoint. No change of reflex was found in other groups. Renal function study demonstrated that both renal hemodynamics and electrolyte excretions were unaltered in all groups.

Conclusion

CsA increased SAP, MAP and DAP. Increased in blood pressure may in part be due to decreased baroreceptor reflex sensitivity. These effects can be prevented by enalapril pretreatment suggesting that blood pressure elevation was mediated via activation of renin angiotensin aldosterone system.