In-vivo visualisation of glomerular filtration by two-photon microscopy in a rat

Abstract

The purpose of this study was to visualise and evaluate glomerular filtration quantitatively under physiological conditions in a rat. We used normal Wistar rats. Various sizes of dextran (3k, 10k, 40k and 70kDa) conjugated with Texas Red in 0.5 ml were administered intravenously by bolus shot and for the next 80 seconds glomerular filtration was observed by two-photon microscopy (Leica TCS SP2). In this way, glomerular filtration was visualised. FITC conjugated 500kDa dextran was administered to dye intravascular area prior to experiment. The time course of Texas Red intensity in Bowman's space was measured off-line later. Intensity peak values were normalised for comparison by the peak value of 3kDa as sieving coefficients. Filtration of the smaller dextrans (MW 3k and 10kDa) was clearly visualized by two-photon microscopy in rats. Filtration of the larger dextrans (MW 40k and 70kDa) was also found indicating leakage of the size of albumin molecule even in a normal rat. Glomerular filtration in a rat was clearly visualised by two-photon microscopy and leakage of larger particles of 70kDa dextran was found even in a normal rat. Two-photon laser microscopy is a powerful tool to investigate renal glomerular functions quantitatively.