摘要 : We examined the activities of some physiologically active substances (enzymes) in human seminal plasma from subjects in their 20s, 30s, and 40s. The average volume of semen per ejaculation in this investigation did not differ sign... 展开 We examined the activities of some physiologically active substances (enzymes) in human seminal plasma from subjects in their 20s, 30s, and 40s. The average volume of semen per ejaculation in this investigation did not differ significantly depending on the age of the subject. Two age dependent patterns of decrease of substances in semen were observed, and the substances including tissue kallikrein and prostate specific antigen (PSA) basic arginine amidase in human seminal plasma showing the first pattern (a significant decrease in the 40s as compared to the 30s) might be initially secreted from the prostate gland, and whereas the glands secreting the other group of substances including active form coagulation factor X (FXa) and plasminogen are not now known. The levels of these substances in semen decrease in the subjects in their 30s. The coagulation and liquefaction times of human semen from older subjects were both prolonged with those of semen from younger subjects, and that such alteractions ultimately cause the age dependent declines of the motility of sperm and the ability of fertility. 收起