ComparativeIn VitroEffects of Calcineurin Inhibitors on Functional Vascular Relaxations of Both Rat Thoracic and Abdominal Aorta

Abstract

Background and Aim. Calcineurin inhibitors (CNIs) have shown to develop hypertension in transplant patients. Thein vitroincubation effects of cyclosporine (CsA) and tacrolimus (Tac) on vascular relaxations of rat thoracic aorta (TA) and abdominal aorta (AA) need to be investigated.Methods. The optimal concentrations of CsA (1.0 mg/mL) and Tac (0.1 mg/mL) used to compare endothelium-dependent (acetylcholine (ACh)) and endothelium-independent (sodium nitroprusside (SNP)) vascular relaxation against the agonists in phenylephrine (PE-) constricted TA and AA of 13-week-old male Sprague Dawley rats (n=6).Results. In TA, the maximal vasodilator response elicited by ACh (control:Imax98%) was significantly (P<0.01) inhibited by CsA (Imax10%) but not by Tac (Imax97%). In AA, (control: IC5050 nM;Imax100%) CsA (IC507 μM; (P<0.01) showed strong sensitivity to inhibit ACh-dependent vascular relaxation than Tac (IC50215 nM (P<0.05);Imax98%). CsA and Tac failed to affect the inhibitory responses to SNP in both TA and AA.Conclusion. CsA exerts profound inhibitory effect on endothelium-dependent vasodilatation as compared to Tac in both TA and AA. Aortic rings from the thoracic region are more sensitive to CNIs, since the vasodilator response to ACh is solely mediated by NO while in the AA, ACh likely recruits other endothelial mediators besides NO to maintain vasodilatation.