Interactions in vitro and in vivo between porcine tissue kallikrein and porcine plasma proteinase inhibitors.

Abstract

The elimination of radio-iodinated porcine tissue kallikrein, after intravenous injection in the pig, showed a rapid initial clearance from plasma (T1/2 approximately 10 min), followed by a phase of slower elimination (T1/2 approximately 100 min). Gel filtration of plasma samples showed complexes with alpha 1-alpha 2-macroglobulin (A1a2-M) and alpha 1-proteinase inhibitor (A1-PI), which decreased with time. The urinary excretion of undegraded tissue kallikrein was about 1.8%. Gel filtration of urine showed a minor peak representing free tissue kallikrein and a major peak representing degradation products. On average, 8.3% was found in the liver and 1.3% in the kidneys post mortem, indicating that these are the primary organs for the elimination of tissue kallikrein. The in vivo findings were supported by in vitro experiments. A1a2-M were found to be the major inhibitors of tissue kallikrein, when a mixture of the enzyme and porcine plasma was analysed by gel filtration, immunoelectrophoresis, crossed immunoelectrophoresis and autoradiography. A1-PI was only a minor inhibitor of tissue kallikrein. Both the A1a2-M and A1-PI complex formation was found to be time-dependent and slow; unbound glandular kallikrein was still detected after 12 h, even when there was a molar surplus of A1a2-M and A1-PI. The complexes with A1a2-M and the unbound tissue kallikrein were found to be enzymatically active against low-molecular-weight chromogenic substrate. The total tissue kallikrein-inhibiting capacity of plasma seemed to be exceeded at a concentration of 800 K U/l when analysed using the rat uterus bioassay.(ABSTRACT TRUNCATED AT 250 WORDS)