Effects of aging and castration on plasminogen activator and metalloprotease activities in the rat prostate complex

Pathology of the prostate gland in rats and humans is associated with aging. Our objective was to examine the effects of aging on the activities of plasminogen activators and metalloproteases in the prostatic complex of rats. Plasminogen activator activities (very low in the anterior, lateral, and dorsal lobes, in contrast to higher activities in the ventral lobe of 4-month-old adult rats) increased with aging in the dorsal and anterior prostate lobes of 31-month-old rats; these activities also increased in the dorsal and lateral lobes upon castration of 18-month-old rats. The plasminogen activator activities in the ventral lobe did not increase with aging to 18 months but did increase 3-5-fold after castration of either young or old rats. Metalloprotease activities of 70 and 76 kDa were observed in the anterior and lateral lobes of 4 month untreated adult rats, whereas the dorsal lobe showed MP of 70 and 92 kDa. Castration of young adult rats increased activities of all three molecular forms of metalloprotease in these three lobes. Increased expression of metalloprotease activities was also found with aging to 31 months in the anterior, lateral, and dorsal lobes. However, changes in metalloprotease activities associated with age were most striking in the lateral lobe and included activities of 52, 55, 81, 93, 113, and 117 kDa at 18 months of age. Castration for 30 days at this age resulted in a decline in the 52, 55, 113, and 117 kDa activities and an increase in activities of the 70, 81, and 93 kDa forms. These latter metalloprotease activities were also increased in the dorsal lobe after castration. Our results suggest that some metalloprotease activities increased in the dorsal lobe after castration. Our results suggest that some metalloprotease activities increased in the lateral lobe with age possibly result from an increased accumulation of secretory proteins (i.e., 52, 55, 113, and 117 kDa), whereas the 70, 81, and 93 kDa metalloprotease activities may be related to possible prostatitis and/or involved in changes in tissue organization. The increased expression of metalloprotease activities in the lateral and dorsal prostate lobes with aging, and castration upon aging, may be indicative of altered hormonal regulation of these proteases in these lobes.