Evaluation of average life span of epithelial and stromal cells of human prostate by superoxide dismutase activity.

Little is known about the cell kinetics on which development of benign prostatic hyperplasia is based. This prompted us to study the superoxide dismutase (SOD) activity, which is known 1) to correlate with the life span of cells and 2) to decrease with advancing age of cells. Therefore, SOD was measured in epithelium and stroma of the human prostate from patients of various ages (20-86 years) and compared with the activity in the postmitotic skeletal muscle. It was found that the highest mean specific SOD activity is present in skeletal muscle (4.0 mU.mg protein-1), followed by the stroma (2.1 mU.mg protein-1) and epithelium (1.4 mU.mg protein-1). Similar results were obtained when SOD activity was expressed per DNA (5.03, 1.73, and 0.16 mU.micrograms DNA-1, respectively). Comparing the slope of the age-dependent regression lines, it was demonstrated that the slope of the stroma is much closer to the slope of the postmitotic skeletal muscle than the slope of the epithelium. From the data, it was calculated that the average life span of stromal cells is probably longer than 30 years and of epithelial cells longer than 2 years. Hence in human prostatic tissue the average cell death rate might be rather low.