[Absorption of swine pancreatic kallikrein in humans]

Porcine pancreatic kallikrein (PPK), the main component of Padutin, has been used in andrology since the beginning of the seventies for the treatment of oligozoospermia and asthenozoospermia. During kallikrein therapy the number of spermatozoa increases, and qualitative and quantitative sperm motility is improved. In order to investigate the intestinal absorption of PPK in man, a clinical study in 26 healthy volunteers was performed. Four of them were given single oral doses of 4500 KU (kallikrein units), the remaining 22 subjects received 600 KU. Serum and urine samples were collected several times within 24 h. Seminal plasma was collected 4-5 days before and 8 h after kallikrein therapy. Absorbed PPK was determined using a highly sensitive bioluminescence-enhanced enzyme immunoassay and a newly developed light-measuring equipment (MTP-reader). In both groups (600 KU and 4500 KU) absorption of PPK in serum was found. The minimum absorption rates were 0.82% and 0.43%, respectively, of the administered PPK, corresponding to an amount of 5 KU per subject. Renal excretion was determined to be 0.27% of the absorbed kallikrein and thus plays only a secondary role in the elimination of PPK from the blood. Moreover, by gel filtration experiments it could be demonstrated that PPK is absorbed in unaltered form and is slowly inhibited in the serum, possibly by a1-proteinase inhibitor. According to our results, kallikrein is absorbed in unaltered form by the intestine. The absorbed amount of PPK is sufficient to exert a possible effect in enzymatically active form on the target cells in the male gonads for several hours.