Renal segmental tubular response to salt during the normal menstrual cycle.
BACKGROUND
It has been suggested that women gain weight and develop peripheral edema during the luteal phase of the menstrual cycle because they tend to retain sodium and water. However, there is actually no clear evidence for physiological, cyclic variations in renal sodium handling during the menstrual cycle. We prospectively assessed the changes in segmental renal sodium handling occurring during the menstrual cycle in response to changes in salt intake.


METHODS
Thirty-five normotensive women were enrolled. Seventeen women were randomized and studied in the follicular and 18 in the luteal phases of their menstrual cycle. All women were assigned at random to receive a low (40 mmol/day) or a high (250 mmol/day) sodium diet for seven days on two consecutive menstrual cycles. Renal sodium handling and hemodynamics were measured at the end of each diet period.


RESULTS
The changes in sodium intake induced comparable variations in sodium excretion in both phases of the menstrual cycle. In the follicular phase, the increase in salt intake was associated with no change in renal hemodynamics, an increased fractional excretion of lithium (FELi) and a decreased fractional distal reabsorption of sodium (FDRNa), suggesting that sodium reabsorption is reduced both in the proximal and the distal tubules. In contrast, in the luteal phase, the renal response to salt was characterized by a significant renal vasodilation and a marked salt escape from the distal nephron, compared to the women investigated in the follicular phase (P < 0.01). Sodium reabsorption by the proximal nephron was not reduced as indicated by the unchanged FELi.


CONCLUSIONS
These results show that the segmental renal handling of sodium differs markedly in the two phases of the menstrual cycle. They suggest that the female hormones modulate the renal handling of sodium at the proximal and distal segments of the nephron in young normotensive women.
Pechère-Bertschi
Antoinette
A
Policlinique de Médecine and Division of Endocrinology, University Hospital, Geneva, Switzerland.
Maillard
Marc
M
Stalder
Hans
H
Brunner
Hans R
HR
Burnier
Michel
M
D000328:Adult; D000450:Aldosterone / Q000097:blood; D009320:Atrial Natriuretic Factor / Q000097:blood; D001794:Blood Pressure / Q000187:drug effects; D005260:Female; D005498:Follicular Phase / Q000378:metabolism*; D006801:Humans; D007686:Kidney Tubules, Distal / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008094:Lithium / Q000378:metabolism; D008183:Luteal Phase / Q000378:metabolism*; D011374:Progesterone / Q000097:blood; D011446:Prospective Studies; D012079:Renal Circulation / Q000187:drug effects; D012083:Renin / Q000097:blood; D017673:Sodium Chloride, Dietary / Q000493:pharmacokinetics*; D014882:Water-Electrolyte Balance / Q000502:physiology
D017673:Sodium Chloride, Dietary; D000450:Aldosterone; D011374:Progesterone; D009320:Atrial Natriuretic Factor; D008094:Lithium; D012083:Renin