Charlotte H Graugaard-Jensen

Urinary concentration does not exclusively rely on plasma vasopressin. A study between genders

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AIM: We investigated the influence of gender on the diurnal regulation of urine production with special focus on vasopressin, oxytocin and prostaglandin E2.

METHODS: Fifteen young women in mid-follicular phase and 22 young men (20-33 y) were included. All participants underwent a 24-h circadian inpatient study under standardized conditions for measurements of plasma vasopressin, oxytocin, sodium and osmolality. Urine was fractionally collected for measurements of electrolytes, aquaporin-2 and prostaglandin E2.

RESULTS: Plasma vasopressin expressed a diurnal rhythm with a nighttime increase in both genders (p<0.001). The ratio between mean daytime and mean nighttime was 1.57 [95% conf. interval: 1.33-1.84] p<0.001 in men, and 1.35 [95% conf. interval: 1.11-1.64] p=0.002 in women. P-vasopressin was higher in males during the night (p<0.05). There was no difference in diuresis (p=0.43), urine osmolality (p=0.12) or aquaporin 2-excretion (p=0.80) between genders. We found a trend towards a higher reabsorption of free water in males (p=0.07). The excretion of prostaglandin E2 was higher in males (p<0.001). There was no diurnal rhythm in p-oxytocin (p=0.37) and no correlation to diuresis, urine osmolality or aquaporin-2 excretions.

CONCLUSION: Similar urinary flows and osmolalities are associated with levels of plasma vasopressin and renal PGE2, which are higher in males than in females. Oxytocin does not seem to play a role in the diurnal urine formation, whereas prostaglandin E2 could represent a mediator of the gender difference, not only as a mediator of the vasopressin response, but also as an independent factor. These findings need further elucidation. This article is protected by copyright. All rights reserved.

TidsskriftActa Physiologica (Online)
StatusUdgivet - 26 jun. 2014

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