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Serum prolactin-binding protein (PRL-BP) of human and rat are identified as IgG
1INSERM U. 352, INSA, Laboratoire de Physiologie-Pharmacodynamie, Villeurbanne, France.
Heterogeneity of circulating prolactin in various species including rat and man is well known. We have recently shown that PRL was able to bind to a protein of high molecular weight in plasma obtained from estradiol treated ovariectomized females rats. This study was undertaken to look for a possible PRL-binding in woman serum and to identify the PRL-BP in both rat and human sera. Pooled sera from normal women taking oral contraception and from women on the 3rd trimester of pregnancy were purified on affinity chromatography column, prepared with sepharose 4B-CNBr coupled to oPRL (ovine PRL). Elution resulted in a protein of 160 kD mol wt when subjected to SDS PAGE in non reducing conditions. Under reducing conditions 2 forms of 50 and 27 kD were found. The 160 kD and the 50 kD forms were able to bind to hPRL. The 3 forms (160, 50 and 27 kD) were recognized by monoclonal antibodies against PRL receptors. Both the 50 and 27 kD forms obtained from rat and human sera were sequenced and revealed to be the heavy and light chain of IgG1. This result was confirmed by specific immunoprecipitation of the PRL-BP by antibodies against human and rat IgG. This study showed, that autoantibodies to PRL were present in rat and human sera, even in physiological conditions such as pregnancy.
Heterogeneity of circulating prolactin in various species including rat and man is well known. We have recently shown that PRL was able to bind to a protein of high molecular weight in plasma obtained from estradiol treated ovariectomized females rats. This study was undertaken to look for a possible PRL-binding in woman serum and to identify the PRL-BP in both rat and human sera. Pooled sera from normal women taking oral contraception and from women on the 3rd trimester of pregnancy were purified on affinity chromatography column, prepared with sepharose 4B-CNBr coupled to oPRL (ovine PRL). Elution resulted in a protein of 160 kD mol wt when subjected to SDS PAGE in non reducing conditions. Under reducing conditions 2 forms of 50 and 27 kD were found. The 160 kD and the 50 kD forms were able to bind to hPRL. The 3 forms (160, 50 and 27 kD) were recognized by monoclonal antibodies against PRL receptors. Both the 50 and 27 kD forms obtained from rat and human sera were sequenced and revealed to be the heavy and light chain of IgG1. This result was confirmed by specific immunoprecipitation of the PRL-BP by antibodies against human and rat IgG. This study showed, that autoantibodies to PRL were present in rat and human sera, even in physiological conditions such as pregnancy.