Renal hemodynamic and tubular responses to salt in women using oral contraceptives.
BACKGROUND
The use of oral contraceptives is associated with an increased risk of developing hypertension but the mechanisms of this hypertensive effect are not completely defined. The purpose of the present study was to assess prospectively the systemic and renal hemodynamic and tubular responses to salt in women taking oral contraceptives.


METHODS
Twenty seven young healthy normotensive women taking oral contraceptives containing monophasic combination of 30 microg ethynilestradiol and 150 microg desogestrel for>6 months were enrolled. All women were assigned at random to receive a low (40 mmol/day) or a high (250 mmol/day) sodium diet for 1 week on two consecutive menstrual cycles during the active oral contraceptive phase. At the end of each diet period, 24-hour ambulatory blood pressure, renal hemodynamics, sodium handling, and hormonal profile were measured.


RESULTS
The blood pressure response to salt on oral contraceptives was characterized by a salt-resistant pattern with a normal circadian rhythm. Salt loading results in an increase in glomerular filtration rate (GFR) (P < 0.05 vs. low salt), with no change in the renal plasma flow, thus leading to an increase in the filtration fraction (P < 0.05). At the tubular level, women on oral contraceptives responded to a low salt intake with a marked increased in proximal sodium conservation (P < 0.01 vs. high salt) and with an almost complete reabsorption of sodium reaching the distal tubule. After sodium loading, both the proximal and the distal reabsorption of sodium decreased significantly (P < 0.01).


CONCLUSIONS
The use of oral contraceptives is not associated with an increased blood pressure response to salt in young normotensive women. However, oral contraceptives affect the renal hemodynamic response to salt, a high salt intake leading to an increase in GFR and filtration fraction. This effect is possibly mediated by the estrogen-induced activation of the renin-angiotensin system. Oral contraceptives also appear to increase the tubular responsiveness to changes in sodium intake. Taken together, these data point out evidence that synthetic sex steroids have a significant impact on renal function in women. The renal effects of oral contraceptives should be taken into account when managing young women with renal diseases.
Pechère-Bertschi
Antoinette
A
Policlinique of Medicine and Division of Endocrinology, Reproduction and Chemical Laboratories University Hospital, Geneva, Switzerland. Antoinette.Pechere@hcuge.ch
Maillard
Marc
M
Stalder
Hans
H
Bischof
Paul
P
Fathi
Marc
M
Brunner
Hans R
HR
Burnier
Michel
M
D000328:Adult; D001794:Blood Pressure / Q000187:drug effects; D003276:Contraceptives, Oral / Q000494:pharmacology*; D004357:Drug Synergism; D005260:Female; D006339:Heart Rate / Q000187:drug effects; D006439:Hemodynamics / Q000187:drug effects; D006728:Hormones / Q000097:blood; D006801:Humans; D007668:Kidney / Q000378:metabolism; D007684:Kidney Tubules / Q000187:drug effects*; D012079:Renal Circulation / Q000187:drug effects*; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology*
D003276:Contraceptives, Oral; D006728:Hormones; D012965:Sodium Chloride; D012964:Sodium