PSP94 (or beta-microseminoprotein) is a secretory protein specifically expressed and synthesized in the lateral lobe of the rat prostate

BACKGROUND. Prostatic secretory protein of 94 amino acids (PSP94), also cal led beta-microseminoprotein, is a small, nonglycosylated protein, rich in c ysteine residues. It was first isolated as a major protein from human semin al plasma. Subsequently, its homologous proteins were identified, and their cDNAs or genes have been cloned in primates, pigs, and rodents. METHODS. The present study investigated the expression pattern of PSP94 in the normal Noble rat prostate gland by nonradioactive in situ hybridization , Northern blotting, RT-PCR, Western blotting, and immunohistochemistry. It s expression in the mouse prostate gland was also examined by in situ hybri dization. RESULTS. The results of in situ hybridization, and Northern and Western blo t analyses, showed that the expression of rat PSP94 was prostate-specific. It was highly expressed in the lateral prostatic lobe, moderate in the dors al lobe, weak in the coagulating gland, and negative in the ventral lobe an d seminal vesicle. Its specific expression in the rat prostate gland was fu rther confirmed by RT-PCR analysis of prostatic and nonprostatic organ tiss ues. Its mRNA transcripts were not detected in the urinary, digestive, and respiratory tracts, male and female reproductive organs, muscles, brain, an d kidney. Its molecular mass was estimated to be 14.5 kDa by Western blotti ng. Similar prostate-specific expression of PSP94 was also observed by in s itu hybridization in the lateral lobe, but not in the dorsal and ventral lo be, of the mouse prostate gland. CONCLUSIONS. Rat PSP94 is a major secretory protein highly expressed and sy nthesized by the lateral lobe of both rat and mouse prostate glands, and mo derately expressed in the dorsal lobe of the rat prostate gland. (C) 2000 W iley-Liss, Inc.