AJP - Regulatory, Integrative and Comparative Physiology, Vol 238, Issue 1 82-R90, Copyright © 1980 by American Physiological Society
Fat-free mass, total body water, and intracellular water in the aged rat
G. T. Lesser, S. Deutsch and J. Markofsky
Total body water (TBW) and intracellular water (ICW = TBW minus
extracellular water), when related to fat-free body mass (FFB), were
recently observed to remain stable in healthy aged men and women. To expand
these findings, a group of male Sprague-Dawley rats was followed from
weaning to death. The design minimized several perturbations common to
aging studies. At about 100-day intervals from 297 to 888 days,
representative animals were killed for chemical studies. TBW/FFB was stable
from 362 to 715 days, then significantly higher at 800 and 888 days.
Extracellular water content of the fat-free body (ECW/FFB) increased
significantly during middle life (362--579 days), then remained stable
through 888 days. Changes of ICW/FFB were not significant. Aside from a
uniquely higher value at 638 days, protein content did not differ
significantly at any age. The stability of these major constituents
suggested approximate maintenance of cell mass in healthy rats at late
ages, a conclusion supported by additional observations of this colony and
of an aged human population. We are unable to confirm the hypothesis that
loss of FFB is part of the normal aging process.
