HUMAN LARGE LUTEAL CELLS IN THE MENSTRUAL-CYCLE AND EARLY-PREGNANCY EXPRESS LEUKOTRIENE A4 HYDROLASE

Leukotriene (LT) A4 hydrolase (EC3.3.2.6) converts LTA4 to LTB4 which shows a chemotactic activity to leukocytes. To investigate the involve ment of LTB4 in human corpus luteum (CL) function, the localization of LTA4 hydrolase in human ovarian tissues was examined by immunohistoch emistry with a rabbit polyclonal antibody against LTA4 hydrolase, The enzyme was weakly expressed on granulosa cells of the follicles. After ovulation, the intensity of LTA4 hydrolase on large luteal cells incr eased and was highest in the midluteal phase. High expression was also observed in the CL of early pregnancy. In theca interna and small lut eal cells, LTA4 hydrolase was weakly detected in all developmental sta ges. Immunoblot analysis demonstrated that the molecular mass of LTA4 hydrolase expressed in CL was 62 kDa, and confirmed that LTA4 hydrolas e expression increased during CL formation and remained high in early pregnancy. The sequence encoding mRNA of LTA4 hydrolase, which was iso lated from CL and amplified by polymerase chain reaction, was shown to be identical to the previously reported one. Immunocytochemistry show ed that LTA4 hydrolase expression in cultured granulosa cells increase d over 4 days in vitro and was enhanced by human chorionic gonadotroph in treatment. These expression profiles of LTA4 hydrolase suggest the involvement of LTB4 in luteal cell function during CL formation and ea rly pregnancy.