AJP - Regulatory, Integrative and Comparative Physiology, Vol 248, Issue 3 282-R287, Copyright © 1985 by American Physiological Society
Changes in anatomy, glomerular filtration, and solute excretion in aging rat kidney
B. Corman, J. Pratz and P. Poujeol
Changes in kidney function were studied in anesthetized female WAG/Rij rats
6, 18, and 30 mo old. The growth in kidney size measured between 6 and 18
mo and 18 and 30 mo was due to enlargement of the glomeruli and lengthening
of the proximal tubules, without significant changes in the number of
nephrons. Glomerular filtration per gram kidney was unaffected between 6
and 18 mo but diminished 27% between 18 and 30 mo. This reduction was
accompanied by an intrarenal redistribution of individual filtration rates
for the superficial and deep nephrons. Fractional excretion of sodium,
potassium, calcium, and magnesium declined sharply between 6 and 18 mo but
did not change further between 18 and 30 mo, whereas the fractional
excretion of amino acids and glucose remained constant between 6 and 18 mo
but rose in the 30-mo group. Taken together, these observations indicate
that, in the rat, kidney aging cannot be reduced to a loss in the number of
functional nephrons but is the result of several differential and specific
processes.
