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Study of molecular heterogeneity of immunoreactive prolactin in patients with macro- and microprolactinomas and idiopathic hyperprolactinemia has shown heterogeneity of the total blood immunoreactive prolactin pool in all the examined patients. This pool included three basic forms with molecular masses about 23, 50, and over 100 kD (23K-, 50K-, 100K-prolactin), whose ratios essentially differed in individual patients. Physiologically the most active monomeric 23K form of prolactin predominated in the blood of patients with hyperprolactinemia due to hypophyseal micro- and macroadenomas, parallelled by manifest signs of galactorrhea and hypogonadism; the content of this form may reach 95% of the total immunoreactive hormone. Patients with hyperprolactinemia of obscure origin present with quite the contrary ratio of prolactin immunoreactive forms with the predominance of high-molecular 100K form of the hormone, whose share may reach 80-90%. Such cases of hyperprolactinemia may be associated with the absence of clear-cut clinical manifestations, including such as galactorrhea and menstrual cycle disorders, and with inefficacy of traditional therapy. Such cases were tentatively classified as 'the high-molecular prolactin syndrome' and need further research.

Highly purified preparation of prolactin with molecular mass 23 kDa, which is the main form of the hormone in human amnionic fluid, was isolated from the fluid using gel filtration on Sephadex G-100, chromatography on DEAE-Sepharose, concanavalin A Sepharose, CM-cellulose. Physico-chemical, immunochemical and biological properties of the amnionic prolactin were studied as compared with those of hypophyseal hormone. Properties of the hormonal forms isolated from both these tissues were similar. The glycosylated form of prolactin with molecular mass 25.0 kDa was detected either in amnionic fluid or in hypophysis.

The level and molecular forms of prolactin (PRL) in amniotic fluid of pregnant women were investigated at various time of pregnancy with the help of radioimmunoassay, electrophoresis in polyacrylamide gel and immune blotting technique using poly- and monoclonal antibodies to human hypophyseal prolactin (PRL). Changes in the level of immunoreactive PRL in amniotic fluid had the shape of a Gaussian curve with a maximum at 22-29 weeks. Amniotic PRL was characterized by molecular polymorphism. A conclusion has been made that amniotic fluid PRL in pregnancy presents an independent pool of hormones, unrelated to hypophyseal PRL.