Prolactin and amniotic fluid electrolytes.

Prolactin (PRL) levels and Na+, K+, Cl-, Ca++ concentrations in maternal serum and amniotic fluid from 64 women in normal term pregnancy were measured by immunoenzymetric assay and flame photometry. The mean amniotic fluid PRL concentration was 597.7 (SE 31.5) ng/ml and the mean amniotic fluid Na+, K+, Cl- and Ca++ levels were 125.6 (SE 0.9) mmol/l, 4.5 (SE 0.1) mmol/l, 109.3 (SE 1.3) mmol/l and 2.0 (SE 7.5 E-02) mmol/l, respectively. There was no correlation between PRL levels in maternal serum and amniotic fluid, and the electrolyte concentrations in amniotic fluid. A close correlation was found between the concentrations of Na+ and Cl- in maternal serum and amniotic fluid. Thus, even though PRL may participate in the regulation of electrolytes in the amniotic fluid compartments, our findings provide indirect evidence for the existence of other regulatory mechanisms.