Histological features of BPH in old and young rats. Young intact rats: ventral prostate—smooth edges of acini, oval shaped with thin walls without folds, and evenly filled with secretion; dorsolateral prostate—smooth edges of acini, of arbitrary shape with thin walls, folding is allowed, and evenly filled with secretion; anterior prostate—large acini and folded two-layer walls. Young BPH rats: ventral prostate—a change in the cell walls of the acini, folding appears, and marked hyperplasia of muscle tissue; dorsolateral prostate—marked hyperplasia of the walls of the acini and muscle tissue; anterior prostate—the wall of the acini with marked hyperplasia. Old intact rats: ventral prostate—signs of BPH appear in the accumulation and ablation of acini and folding is detected; dorsolateral prostate—a low content of secretion and folding of the walls; anterior prostate—signs of BPH: focal high folding. Old BPH rats: ventral prostate—focal folding of acini and muscle hyperplasia; dorsolateral prostate—marked hyperplasia of muscle tissue and thickening of the walls; anterior prostate—the walls of the acini and muscle tissue with severe hyperplasia.