AJP - Renal Physiology, Vol 250, Issue 6 1055-F1062, Copyright © 1986 by American Physiological Society
Activities of cathepsins B and L in isolated nephron segments from proteinuric and nonproteinuric rats
C. J. Olbricht, J. K. Cannon, L. C. Garg and C. C. Tisher
The intralysosomal proteinases cathepsins B and L were measured in
microdissected segments of rat nephron. Z-Arg-Arg-NMec served as the
substrate for cathepsin B and Z-Phe-Arg-NMec for cathepsin B and L
together. Individual S1, S2, and S3 segments of proximal tubules, TDL,
MTAL, CTAL, DCT, CCD, and OMCD were dissected from young female rats
weighing 130 +/- 11 g with low protein excretion (0.68 +/- 0.1 mg/24 h),
from older female rats weighing 289 +/- 9 g with protein excretion of 10
+/- 6.3 mg/24 h, from older male rats weighing 404 +/- 11 g with protein
excretion of 22 +/- 6 mg/24 h, from female rats weighing 198 +/- 10 g with
albumin-induced proteinuria (411 +/- 134 mg/24 h), and from female rats
weighing 203 +/- 11 g with low protein excretion (2.7 +/- 0.4 mg/24 h). The
distributions of cathepsin activities along the nephron were similar. In
all five groups, S1 and S2 segments had enzyme activities three times
higher than in all remaining segments. In S2 and S3, enzyme activities were
two to three times higher in proteinuric animals. These findings suggest
that in proteinuric animals the increase in the protein load delivered to
the proximal tubules selectively stimulated cathepsin activities in the S2
and S3 segments, presumably because of an increase in protein uptake, and
that cathepsins B and L participate in lysosomal digestion of protein
reabsorbed from the glomerular filtrate via endocytosis.
