Sodium depletion of pregnant ewes and its effects on foetuses and foetal fluids

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Abstract
Some effects of sodium depletion were investigated in sheep at different stages of pregnancy (from 55 to 139 days). Sodium depletion was induced by draining the saliva from one parotid gland for a period of 6 days. Fetal samples were collected at the end of the depletion period. Sodium depletion of the ewe resulted in a fall in saliva Na+ level and a rise in saliva K+ level, a fall in plasma Na+ and K+ levels, a 35% reduction in plasma volume and a 16% reduction in body weight. In the Na+ depleted ewes the sodium levels of the fetal plasma and amniotic fluid were lower and the volume of the allantoic fluid greater than those in the control ewes. It is concluded that sodium depletion of the ewe leads to a deficiency of sodium in the fetus. On the basis of these experiments and other reports it is postulated that a sodium deficient fetus, like a sodium deficient adult, responds to the deficiency by restricting sodium losses in the urine and by excreting water.