Immunoreactive prolactin like material in the urine of women

Abstract

Immunoreactive prolactin-like material (Ir Prl) was detected in urines of eugonadal women during the luteal phase and in urines of pregnant and lactating women. The levels of Ir Prl urinary excretion per 24 h and of elimination per 100 ml of glomerular filtrate were highest in lactating women as compared to pregnant women; levels in pregnant women were elevated as compared to eugonadal subjects. Iv injection of thyrotropin releasing hormone (TRH, 200 μg) caused increased levels of urinary Ir Prl. The physicochemical characteristics of urinary Ir Prl of lactating women were investigated by filtrating urine samples on Ultragel Aca 54 in presence or absence of Trasylol. Urines, supplemented with Trasylol and analyzed either immediately or after storage at room temperature for 24 h, contained in addition to the 23,000 Mr monomeric form (25.2+7.4%), two fractions of high (≥ 70,000) or low (< 23,000) molecular weight, respectively. The latter material largely predominated (73.5±7.3%). Urines kept at room temperature for 24 h without Trasylol showed variable but significant decreases in the monomer form with a parallel increase in high MW and fragmented forms. The extent of degradation of the monomer was directly proportional to the proteolytic activity of the urines as estimated by the Azocoll breakdown test. Contrary to what was observed with the urinary endogenous monomeric Prl, human pituitary Prl.remained unaltered upon incubation in Trasylol-free urines up to 45 h. These experiments suggest that Prl when it is excreted in the urine, undergoes varying modifications which give rise to immunoreactive aggregates, fragments and a material of normal molecular weight but of high sensitivity to the action of the urinary proteases.