Cysteine proteinase inhibitors in human and rat male sex glands.

The testis and prostate of men had two types of cysteine proteinase inhibitors of different isoelectric point (pI = 4.5 and 6.3) and molecular masses (90,000 and 12,000). The seminal vesicle contained not only these two inhibitors but also a basic inhibitor with a pI = 9.5 and Mr 11,000. In rats, the inhibitors in the testis and prostate consisted of two types with pI values of 4.3 and 4.8 and Mr 90,000 for both. In addition to these two inhibitors, the seminal vesicle contained large amounts of two basic inhibitors with pI values of 7.5 and 8.3 and Mr of 11,000 for both. We suggest that the basic cysteine proteinase inhibitor found in semen might be excreted from or be modified in the seminal vesicle.