Rhodamine 123 accumulates extensively in the isolated perfused rat kidney and is secreted by the organic cation system

Abstract

Rhodamine 123 has been shown to be a substrate for P-glycoprotein in multidrug resistant cells, In the present investigation the disposition of rhodamine 123 was studied in the isolated perfused rat kidney, After exposing the kidneys to perfusate concentrations ranging from 10 to 1000 n g/m l, the renal clearance was 4-1 times the clearance by glomerular filtration, respectively, indicating active and saturable secretion of rhodamine 123. The rate-limiting step in secretion was found to be membrane passage from cell to tubular lumen. Suprisingly, renal clearance was not influenced by the P-glycoprotein inhibitors cyclosporin A or digoxin. However, pretreatment o f the kidneys with verapamil and quinidine (inhibitors of both P-glycoprotein and organic cation transport) or cimetidine (organic cation transport inhibitor) resulted in a significantly reduced rhodamine 123 clearance, indicating that the renal organic cation carrier may be involved in active secretion. Rhodamine 123 accumulated extensively in the isolated perfused rat kidney; tissue concentrations o f 2 7 0 -3 6 0 times the perfusate concentration were determined. Similar accumulation ratios at different perfusate concentrations were found, suggesting that the compound enters the tubular cells by (facilitated) diffusion. In conclusion, rhodamine 123 accumulated extensively in the isolated perfused rat kidney and active renal secretion appears to be pi*eferentially mediated by the organic cation carrier and not by P-glycoprotein.

Interactions of attention-deficit/hyperactivity disorder therapeutic agents with the efflux transporter P-glycoprotein

“…did not decrease the P app B-A -to-P app A-B ratio to around 1.00. Our current data are not sufficient to provide a firm explanation of this phenomenon, but we speculate that it might be caused by the participation of other transporters in rhodamine123 transport since rhodamine123 has been reported to be also the substrate of other transporters such as OCTs (Masereeuw et al, 1997;van der Sandt et al, 2000).…”

“…However, it should be noted that, in addition to P-glycoprotein, other transporters (e.g. mutant BCRP and OCTs) have also been reported to transport rhodamine123 across the cellular membrane (Alqawi et al, 2004;Masereeuw et al, 1997;van der Sandt et al, 2000). van der Sandt and coworkers (2000) reported that rhodamine123, but not doxorubicin, could be transported by OCTs expressed in LLC-PK1 cells.…”

Examination of the Functional Activity of P-glycoprotein in the Rat Placental Barrier Using Rhodamine 123

“…To confirm this speculation, the pharmacokinetics of Rho123 across the dually perfused rat placenta in situ was investigated. Rhodamine 123, a fluorescent dye, is a well established model compound for the evaluation of the transport activity of P-gp in different sites of the body and for testing of tumor cells for MDR mediated by P-gp (Ludescher et al, 1992;Masereeuw et al, 1997;de Lange et al, 1998;Yumoto et al, 1999;van der Sandt et al, 2000). Nevertheless, some authors suggest that a rOCT could also participate in Rho123 transport (Masereeuw et al, 1997;van der Sandt et al, 2000).…”

“…Rhodamine 123, a fluorescent dye, is a well established model compound for the evaluation of the transport activity of P-gp in different sites of the body and for testing of tumor cells for MDR mediated by P-gp (Ludescher et al, 1992;Masereeuw et al, 1997;de Lange et al, 1998;Yumoto et al, 1999;van der Sandt et al, 2000). Nevertheless, some authors suggest that a rOCT could also participate in Rho123 transport (Masereeuw et al, 1997;van der Sandt et al, 2000). To assess the permeability of the intact placental barrier for Rho123, transplacental passage of Rho123 across the placenta was expressed as the transplacental clearance per the wet weight of the placenta (milliliters per minute per gram).…”

“…A fluorescent dye rhodamine 123 (Rho123), which is a well established model substrate for testing the functional transport activity of P-glycoprotein, was used (Masereeuw et al, 1997;van der Sandt et al, 2000). CsA, PSC 833 (a nonimmunosuppressive derivate of CsA), and chlorpromazine were used as selective inhibitors/modulators of P-gp, quinidine was used as a nonselective inhibitor for both P-gp and organic cation transporters (rOCT), and sodium azide was used as an inhibitor of ATP mitochondrial synthesis.…”