The renin-aldosterone response to stimulation and suppression during normal pregnancy.
OBJECTIVE
During normal pregnancy, studies have shown increased activity of the renin-angiotensin-aldosterone system (RAAS) and a dissociation of plasma renin activity (PRA) and aldosterone (Aldo) evidenced by a greater increase in Aldo relative to PRA. The aims of this study were to examine the RAAS response to stimulation by upright posture and suppression by saline infusion and to investigate the PRA-Aldo dissociation under these two conditions.


METHODS
We studied 24 healthy normotensive women (mean+/-standard error of mean, ages 29+/-1 yrs) in sodium (Na) balance in the second and third trimesters and postpartum. Subjects underwent a 24-hour urine collection which was analyzed for Na, norepinephrine (NE), epinephrine (Epi), and dopamine (DA); a posture study with analysis of blood pressure (BP), PRA, Aldo, NE, Epi, DA, and cortisol; and a 0.9% NaCl infusion study (500 mL/hr for 3 hrs) with analysis of BP, PRA, Aldo, cortisol, and digitalis-like factor (DLF). Analyses included paired t tests to compare posture and saline responses, repeated measures to compare across periods, and percent change to evaluate the PRA-Aldo dissociation.


RESULTS
During pregnancy, PRA, Aldo, BP, catecholamines, and cortisol levels were significantly greater in upright than left lateral decubitus (LLD) posture, and the percent change in Aldo was significantly greater than the percent change in PRA. During pregnancy in response to saline infusion, BP did not change; the PRA and Aldo significantly decreased; the percent change in Aldo was significantly greater than the percent change in PRA in the second trimester; and serum DLF and cortisol levels significantly decreased.


CONCLUSIONS
In longitudinally studied normal pregnancy, PRA and Aldo levels were dissociated at baseline, with stimulation and, to a lesser degree, with suppression. Norepinephrine, adrenocorticotrophic hormone, and DLF may contribute to this dissociation, and clarification of these interactions may provide insight into the regulation of aldosterone during normal and hypertensive pregnancy.
Bentley-Lewis
Rhonda
R
Division of Endocrinology, Diabetes, and Hypertension, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA.
Graves
Steven W
SW
Seely
Ellen W
EW
D000328:Adult; D000450:Aldosterone / Q000378:metabolism* / Q000652:urine; D001795:Blood Pressure Determination; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016014:Linear Models; D008137:Longitudinal Studies; D010298:Parity; D049590:Postpartum Period / Q000378:metabolism / Q000652:urine; D011247:Pregnancy / Q000187:drug effects / Q000502:physiology*; D011262:Pregnancy Trimester, Second; D011263:Pregnancy Trimester, Third; D011295:Prenatal Care; D011336:Probability; D012016:Reference Values; D012083:Renin / Q000378:metabolism* / Q000652:urine; D012084:Renin-Angiotensin System / Q000187:drug effects* / Q000502:physiology*; D012965:Sodium Chloride / Q000008:administration & dosage*; D016482:Urinalysis; D014882:Water-Electrolyte Balance
D012965:Sodium Chloride; D000450:Aldosterone; D012083:Renin