Renal cortical na-,k--atpase activity and abundance is decreased in
normal pregnant rats.
Mahaney, J., C Felton, D Taylor#, W Fleming#, Jq Kong# and C Baylis.
Departments of Physiology, Biochemistry*, and Pharmacology and
Toxicology#, West Virginia University, Morgantown, WV 26506-9229
APStracts 5:0151F, 1998.
During late pregnancy the rat undergoes massive plasma volume
expansion due to cumulative renal sodium retention. In the present
studies, conducted in virgin, mid- (day 11-13) and late (day 18-20)
pregnant rats, we measure Na-, K--ATPase activity (by coupled enzyme
assay) and abundance of the a-subunits of the Na-, K--ATPase (by
Western and slot blot analysis), in kidney cortex, medulla and brain
stem. Unexpectedly, Na-, K--ATPase in renal cortex in both stages of
pregnancy is reduced vs the virgin, consistent with our finding of
reduced quantity of the a-1 subunit. In renal medulla there is a
small rise in activity at mid-term but no difference in either
activity or abundance of the a-1 subunit in late pregnancy, when
renal Na retention is maximal. In brain stem where only a-2 and a-3
subunits are evident, pregnancy has no impact on enzyme activity or
abundance of either isoform. In conclusion, the outcome of these
experiments is unexpected in that we do not observe an increased
renal Na-, K--ATPase activity in late pregnancy and in fact, in renal
cortex, Na-, K--ATPase activity and abundance is reduced. Whatever
promotes net sodium retention in pregnancy must be capable of
overwhelming this and several other strong natriuretic signals.
Received 26 January 1998; accepted in final form 20 August 1998.
APS Manuscript Number F16-8.
Article publication pending Am. J. Physiol. (Renal Physiology).
ISSN 1080-4757 Copyright 1998 The American Physiological Society.
Published in APStracts on 21 September 1998