In 1936, Ehrhadt reported a prolactin-like substance which has been identified as a second protein hormone exists in extracted substance from the placenta. To date various reports have been published, but there are still unsolved problems concerning the specifity of the substance, and its clinical significance is unclear. The purpose of this project was to purify and investigate the biochemical, immunological properties of HPL, and try to localize HPL secretion immunohistologically.
The biological properties examined by intramuscular and intradermal pigeon crop sac reactions, both showed positive results. Biochemical properties were tested by 7.5 % polyacrylamide disc electrophoresis and Free Fatty Acid mobilization. By these methods, the former showed a single band by electrophoresis with purified HPL 200 μg, and the latter showed a strong positive reaction both in vivo and in vitro. Immunological propertiese were examined by immunoelectrophoresis and the Ouchterlony method. In immunoelectrophoresis, the reaction of purified HPL 80 μg and anti-HPL serum resulted in a single strong zone. In contrast, anti-serum and HGH resulted in a weak zone of reaction. We confirmed that HGH cross reacts with our anti-HGH serum to HPL. The cross reaction of HGH with anti-HPL serum was reported by Josimovich et al, and other workers. In the Ouchterlony method, no precipitation line was detected between anti-HPL serum and 50-300 iu of HCG (PREGNYL). The results of investigating the localization of secrtions of HPL immunohistologically, show that the specific fluorescence was limited to the strong reacting syncytial layer in the both the early chorionic villi of normal pregnancy and in the late stages of pregnancy. And the results of examining the localization with enzyme reactions with peroxdase from horseradish Type II, the reaction of benzidine brown was limited to the syncytial trophoblastic layer as in the case of FITC. These results suggests that the localization of the secretion of HPL exists in the syncytial layer of the chorionic villi.