In vivo assessment by videomicroscopy of acute renal microvascular responses to cyclosporin.

Nephrotoxicity limits the use of cyclosporin A for immunosuppression after organ transplantation and may be caused by glomerular hypoperfusion. Indirect studies have shown that cyclosporin A increases renal vascular resistance and reduces total renal blood flow. This study used direct in vivo videomicroscopy to define the effects of the drug on the renal microcirculation of the rat. An intravenous infusion of cyclosporin A (20 mg per kg body-weight) caused a 13 per cent acute constriction of the proximal interlobular artery and an associated 29 per cent reduction in preglomerular interlobular arterial blood flow. There was a simultaneous increase in mean arterial blood pressure of 34 per cent caused by cyclosporin A and a 23 per cent increase in systemic vascular resistance. Cyclosporin acutely reduces renal microvascular blood flow by vasoconstriction and affects the central circulation, suggesting that a generalized peripheral vasoconstriction is induced.