Organic cation transport in the rat kidney in vivo visualized by time-resolved two-photon microscopy.
Secretion of cationic drugs and endogenous metabolites is a major function of the kidney accomplished by tubular organic cation transport systems. A cationic styryl dye (ASP(+)) was developed as a fluorescent substrate for renal organic cation transporters. The dye was injected intravenously and continuously monitored in externalized rat kidneys by time-resolved two-photon laser scanning microscopy. To investigate changes in transport activity, cimetidine, a competitive inhibitor of organic cation transport was co-injected with ASP(+). Shortly after injection, fluorescence increased in peritubular capillaries. Simultaneously, fluorescence was transiently found at the basolateral membrane of the proximal and distal tubules at a higher intensity and shorter wavelength indicating membrane association of ASP(+). Subsequently, intracellular fluorescence increased steeply within 10 s. In the proximal tubules, intracellular fluorescence decreased by 50% within 5 min, while in the distal tubules the fluorescence decreased by only 5% within the same time frame. Intracellular uptake of ASP(+) into proximal tubules was significantly reduced by cimetidine. Our studies show that organic cation transport of the kidney can be visualized in vivo by two-photon laser scanning microscopy.
Hörbelt
M
M
Department of Nephrology, School of Medicine, University Hospital, Essen, Germany.
Wotzlaw
C
C
Sutton
T A
TA
Molitoris
B A
BA
Philipp
T
T
Kribben
A
A
Fandrey
J
J
Pietruck
F
F
D000818:Animals; D001692:Biological Transport; D002412:Cations / Q000378:metabolism; D002927:Cimetidine / Q000494:pharmacology; D005456:Fluorescent Dyes / Q000008:administration & dosage / Q000378:metabolism*; D007275:Injections, Intravenous; D007668:Kidney / Q000098:blood supply / Q000187:drug effects / Q000378:metabolism*; D007686:Kidney Tubules, Distal / Q000378:metabolism; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D008297:Male; D008833:Microcirculation / Q000378:metabolism; D018613:Microscopy, Confocal; D036641:Microscopy, Fluorescence, Multiphoton; D018715:Microscopy, Video; D027701:Organic Cation Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011726:Pyridinium Compounds / Q000008:administration & dosage / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D015203:Reproducibility of Results; D013997:Time Factors
C032315:4-(4-dimethylaminostyryl)-1-methylpyridinium; D002412:Cations; D005456:Fluorescent Dyes; D027701:Organic Cation Transport Proteins; D011726:Pyridinium Compounds; D002927:Cimetidine