Background: Group II phospholipase A2 (PLA2) is a lipolytic enzyme suggested to play a role in inflammation and antibacterial defence. In seminal fluid, the concentration of PLA2 is exceedingly high under normal circumstances (about 1,000 times the concentration in blood plasma of healthy humans). To elucidate the origin of the enzyme present in seminal plasma, we investigated the expression of group II PLA2 in male reproductive organs both at protein and mRNA levels. In addition, the presence of the enzyme was studied in common male genital tumors.
Methods: The methods used were immunocytochemistry, in situ hybridization, and Northern blotting.
Results: Northern blotting gave positive results for group II PLA2 mRNA in normal prostate, whereas other normal genital tissues gave negative results. Immunohistochemistry and in situ hybridization of group II PLA2 gave identical results. The enzyme was produced exclusively by the secretory epithelial cells of the prostatic gland. Surprisingly, expression was restricted to the posterior lobe and paraurethral glands of the prostate. Cells of prostatic adenocarcinoma expressed group II PLA2, whereas cells of other male genital tumors contained neither the enzyme protein nor the mRNA of group II PLA2. In some cases prostatic cancer cell seemed to express group II PLA2 at a higher rate than normal prostatic gland cells.
Conclusions: The high content of group II PLA2 in seminal plasma is due to the local production and secretion of the enzyme by the epithelial cells of the prostatic glands. Group II PLA2 is expressed focally, suggesting that specialized prostatic glands secrete this enzyme. All prostatic adenocarcinomas tested expressed group II PLA2 in variable amounts.