Structure and concentrating ability of the mammalian kidney:
correlations with habitat.
Beuchat, Carol A.
Department of Biology, San Diego State University, San Diego, CA
92182-0057
APStracts 2:0243R, 1995.
Mammals with relatively long loops of Henle for their size tend to
have greater than average urinary concentrating ability, but the
relationship between urine osmolality (Uosm) and absolute loop length
is neither proportional nor direct. Uosm is independent of the length
of the medullary thick ascending limb, which scales similarly with
body mass in animals from mesic, arid, and freshwater environments.
After correcting for the effect of body size, there is a significant
relationship between the length of the thin ascending limb and
concentrating ability, but only in species from mesic environments,
and for these the length of the thin limb accounts for only 16% of
the interspecific variability in Uosm. The absolute length of the
loop of Henle in marine mammals is surprisingy short, yet they
produce very concentrated urine for their size. A functional
dependence of urinary concentrating ability on the length of the loop
of Henle is a central tenant of countercurrent multiplier theory, but
the correlation of maximum urine concentration with loop length is
weak at best and largely reflects the influence of the thin ascending
limb.
Received 11 August 1994; accepted in final form 22 August 1995.
APS Manuscript Number R447-4.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 15 September 1995.