Multiple factors influence glomerular albumin permeability in rats.
Different laboratories recently reported incongruous results describing the quantification of albumin filtration using two-photon microscopy. We investigated the factors that influence the glomerular sieving coefficient for albumin (GSC(A)) in an effort to explain these discordant reports and to develop standard operating procedures for determining GSC(A). Multiple factors influenced GSC(A), including the kidney depth of image acquisition (10-20 μm was appropriate), the selection of fluorophore (probes emitting longer wavelengths were superior), the selection of plasma regions for fluorescence measurements, the size and molecular dispersion characteristics of dextran polymers if used, dietary status, and the genetic strain of rat. Fasting reduced the GSC(A) in Simonsen Munich Wistar rats from 0.035±0.005 to 0.016±0.004 (P<0.01). Frömter Munich Wistar rats had a much lower GSC(A) in both the fed and the fasted states. Finally, we documented extensive albumin transcytosis with vesicular and tubular delivery to and fusion with the basolateral membrane in S1 proximal tubule cells. In summary, these results help explain the previously conflicting microscopy and micropuncture data describing albumin filtration and highlight the dynamic nature of glomerular albumin permeability.
Division of Nephrology, Department of Medicine, Indiana Center for Biological Microscopy, Indiana University School of Medicine, Indianapolis, IN 46202, USA.
Ruben M
RM
Sandoval
Mark C
MC
Wagner
Monica
M
Patel
Silvia B
SB
Campos-Bilderback
George J
GJ
Rhodes
Exing
E
Wang
Sarah E
SE
Wean
Sherry S
SS
Clendenon
Bruce A
BA
Molitoris
D000418:Albumins / Q000378:metabolism*; D000818:Animals; D002463:Cell Membrane Permeability / Q000502:physiology*; D003911:Dextrans; D004032:Diet; D005260:Female; D005456:Fluorescent Dyes; D007678:Kidney Glomerulus / Q000166:cytology* / Q000502:physiology*; D007687:Kidney Tubules, Proximal / Q000166:cytology* / Q000502:physiology*; D008297:Male; D036641:Microscopy, Fluorescence, Multiphoton; D023421:Models, Animal; D011677:Punctures; D051381:Rats; D017207:Rats, Sprague-Dawley; D017208:Rats, Wistar; D013997:Time Factors
D000418:Albumins; D003911:Dextrans; D005456:Fluorescent Dyes