The binding spectra of rat renal and hepatic microsomal cytochromes P-450 with cyclosporine A.

Binding difference spectra of rat renal and hepatic cytochromes P-450 with cyclosporine A (CsA) were measured. In both cases reversed type I spectra were found with the absorbance maximum at 416 nm and minimum at 378 nm. Apparent spectral dissociation constant Kd and maximal absorbance difference delta Amax416-378 did not change substantially with the concentration of the CsA stock solution used. The results suggest that CsA might be biotransformed not only in the liver but also in the kidney.