The dependence of human decidual prolactin production and secretion on the osmotic environment in vitro

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Abstract
Human decidual tissue from uncomplicated term pregnancies was incubated in vitro using a cross-over design of incubation lasting for 72 h. The decidual tissue of each membrane was added sequentially to media with the osmolalities 252, 315 and 387 mmol/kg, and the different osmolalities were in 33 experiments induced by changing the concentration either of NaCl, KCl, mannitol, sucrose, or choline chloride. At 387 mmol/kg all substances elicited a significant increase in prolactin [Prl] secretion compared with the 315 mmol/kg media (14-27%) or the 252 mmol/kg media (26-46%). When the NaCl, KCl, sucrose, and choline chloride media at 387 mmol/kg were compared in another 7 experiments, KCl increased Prl secretion more effectively than the others (10%, P < 0.05). The incubation cross-over design did not permit determination of the decidual Prl content after incubation in each of the various media, but in 28 experiments the mean decidual Prl content was 12.7 mIU/100 mg dry tissue (range 4-30) before and 8.7 mIU/100 mg dry tissue (1-17) after the experiments. The mean amount of Prl secreted during the successive incubations was 152.2 mIU/100 mg dry tissue (19-672) which showed the secretion to be a result of continued Prl production. The effect of osmolality was independent of the basal production rate. The intracellular ionic concentrations, probably of K ion or of Cl ion, are of importance in the regulation of the synthesis and secretion of decidual Prl in vitro.