A Measurement of Immunoreactive Prolactin in the Decidual and Vinous Tissues of Early Pregnancy, and a Comparison with the Prolactin in the Amniotic Fluid

Abstract

Several reports have revealed that human prolactin increases during pregnancy, not only in maternal and fetal serum but also in the amniotic fluid. The source and the role of prolactin in the amniotic fluid however, have not been clear up to now.
In their incubation experiment, Riddick et al (29) proved that decidual tissue at term could secret immunoreactive prolactin (IR-PRL). In order to investigate the source of PRL in the amniotic fluid, we extracted IR-PRL from decidual or villous tissue in early normal pregnancies and measured it by a double antibody radioimmunoassay in this experiment.
The results were the following :
1) We were able to measure IR-PRL from decidual or villous tissue in early pregnan-cy, the dilution curve of which paralleled pituitary standard prolactin. The cross reaction of a PRL standard preparation with HCG and HPL was not recognized within 10 μg/ml.
2) In human decidual tissue, the IR-PRL concentration began to increase at about the sixth week, arrived at the peak value, 81.06 ± 2.13 ng/0.1 g dry weight (d.w.) in the eighth week, and did not change significantly after that. In human villous tissue, although the IR-PRL concentration was distinctly lower than it was in the decidual tissue, it increased gradually and reached the level of 37.44 ± 7.16 ng/0.1g d.w. in the tenth week.
3) The extracted material (IR-PRL) from these two tissues in the 8th week, amniotic fluid at term, and pituitary standard PRL were passed through a Sephadex G-100 column (2×93 cm) with phosphate buffer and saline (0.01M, PH 7.4). In the chromatogram of these four test materials, one peak of IR-PRL was observed. The peak of IR-PRL of decidual and villous tissues and amniotic fluid revealed almost the same fraction number but elevated after the pituitary PRL preparation.
4) By gel filtration, the IR-PRL was able to be differentiated from HCG but not from HPL. The peak of HCG appeared earlier than the peak of IR-PRL and HPL.
5) The distribution of IR-PRL between human decidual and villous tissues was significantly different from that of HPL. IR-PRL concentration was higher in the decidual tissue than in the villous tissue, while HPL concentration was higher in the villous tissue than it was in the decidual tissue. From this observation, we could consider that the sources of these two hormones were different.
The results of these experiments suggest that one of the sources of PRL in the amniotic fluid was the decidual tissue.