Role of hemodynamic factors in osmoregulatory alterations of rat pregnancy.
Plasma osmolality (Posmol) decreases in pregnancy, possibly because of hemodynamically mediated arginine vasopressin (AVP) secretion, i.e., inadequate vascular filling and/or decreased blood pressure. This hypothesis was tested in Sprague-Dawley rats treated on gestational days 1-18 or 13-18 with 1) deoxycorticosterone acetate (DOCA) + standard chow (0.5% Na), 2) vehicle + standard chow, or 3) high-Na (1.25%) diet. Renal sodium "escape" and suppression of the renin-aldosterone system suggested "effective volume expansion," yet Posmol was similar in all pregnant groups, 7-10 mosmol/kg below levels in virgin controls, and plasma AVP was unaltered. Apparent osmotic thresholds for AVP secretion, similar in control and DOCA-treated gravid animals, were 8-10 mosmol/kg below those of untreated virgin rats. Norepinephrine + DOCA, administered to gravid animals consuming normal or high-Na chow, increased blood pressure approximately 10% above control levels, but this also failed to alter Posmol. These data suggest that mechanisms other than hemodynamically mediated AVP secretion are responsible for the osmoregulatory alterations accompanying rodent pregnancy.
Barron
W M
WM
Department of Medicine, Pritzker School of Medicine, University of Chicago, Illinois 60637.
Dürr
J A
JA
Schrier
R W
RW
Lindheimer
M D
MD
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003900:Desoxycorticosterone / Q000494:pharmacology; D004837:Epinephrine / Q000097:blood; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics; D007668:Kidney / Q000187:drug effects / Q000502:physiology*; D009318:Natriuresis / Q000187:drug effects; D009638:Norepinephrine / Q000097:blood / Q000494:pharmacology; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000502:physiology*; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values; D012083:Renin / Q000097:blood; D012982:Sodium, Dietary / Q000494:pharmacology; D014882:Water-Electrolyte Balance
D012982:Sodium, Dietary; D003900:Desoxycorticosterone; D012083:Renin; D009638:Norepinephrine; D004837:Epinephrine