Nitric oxide synthase isoforms in the rat kidney during pregnancy.
OBJECTIVE
Nitric oxide mediates renal vasodilation and hyperfiltration during pregnancy in conscious rats through the endothelin B (ETB) receptor subtype. We tested the hypothesis that immunoreactive levels of endothelial nitric oxide synthase (eNOS) would be greater in the kidneys of midterm pregnant rats compared with virgin rats.


METHODS
We studied midterm pregnancy because renal plasma flow and glomerular filtration rate are maximal at this gestational stage. Western analysis was used to determine the level of eNOS in the three major zones of the kidney-inner medulla, outer medulla, and cortex-and in isolated small renal arteries, and in purified renal microvessels from the cortex.


RESULTS
There were no significant differences in eNOS expression between virgin and midterm pregnant rats in any of those renal tissues, regardless of whether immunoreactivity was expressed as arbitrary densitometry units, as "microg placental equivalents" interpolated from the linear portion of a dose-response curve of placental villous protein (2.5-30 microg, positive control) run concurrently on each gel, or normalized for beta-actin. We also investigated other NOS isoforms. In particular, immunoreactive neuronal NOS (nNOS) was detectable in the inner and outer medulla, but it was not significantly different between groups. nNOS immunoreactivity was below the level of detection in the cortex, but mRNA expression was not significantly different between pregnant and virgin rats by reverse transcriptase polymerase chain reaction.


CONCLUSIONS
Our results suggest that an increase in eNOS isoform mass does not contribute to the endothelin and NO-dependent renal vasodilation in rat gestation.
Novak
Jacqueline
J
Department of Obstetrics, Gynecology and Reproductive Sciences, University of Pittsburgh School of Medicine and Magee-Women's Research Institute, 204 Craft Avenue, Pittsburgh, PA 15213, USA.
Rajakumar
Augustine
A
Miles
Theresa M
TM
Conrad
Kirk P
KP
D000818:Animals; D005260:Female; D007527:Isoenzymes / Q000378:metabolism*; D007668:Kidney / Q000201:enzymology*; D019001:Nitric Oxide Synthase / Q000235:genetics* / Q000378:metabolism*; D052250:Nitric Oxide Synthase Type III; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley
D007527:Isoenzymes; D012333:RNA, Messenger; D019001:Nitric Oxide Synthase; D052250:Nitric Oxide Synthase Type III; C496316:Nos3 protein, rat