Studies on the Release of Tissue Kallikrein in Experimental Pancreatitis in the Pig

Abstract

The activation of the kallikrein-kinin system is thought to be one of the pathophysiological factors in acute pancreatitis. A radioimmunoassay for porcine, pancreatic tissue kallikrein was developed and used to measure levels in normal plasma and peritoneal fluid and in experimental, bile-induced (group and bile trypsin-induced (group B) acute pancreatitis in the pig. Normal porcine plasma and peritoneal fluid contained about 2.17 ± 0.11 and 1.91 ± 0.19 µg/l (SEM) tissue kallikrein, respectively. In experimental, acute pancreatitis there was a rapid rise in the plasma level of tissue kallikrein, followed by a slow increase to a final value of about 150% of the normal plasma level in both groups. In the peritoneal exudate a large increase (200-fold in group A and 2,000-fold in group in tissue kallikrein was seen, with a maximum within about 1/3 of the survival time, followed by a slow decrease until death in group B. In group A a smaller second peak was seen at about 2/3 of the survival time. Gelfiltration of peritoneal exudates showed complexes with alpha₁-, alpha₂-macroglobulin (α₁α₂-M), and alphai-proteinase inhibitor (α₁-PI) and a large portion of free tissue kallikrein. The complexes with α₁α₂-M and the free tissue kallikrein were found to be enzymatically active when tested on chromogenic tripeptide substrate. The presence of large amounts of free and active tissue kallikrein in the peritoneal exudate leads us to the conclusion that tissue kallikrein may be a major cause of local release of kinins in acute pancreatitis.

Turnover of125I-labelled tissue kallikrein following intraduodenal or intravenous administration

“…Blood sampling from the liver veins would have revealed that, but such sampling was regarded as too hazardous and inconvenient for the volunteer. Intravenous injection of radiolabelled tissue kallikrein may mimic the release of tissue kallikrein seen in in¯ammatory disorders such as acute pancreatitis [7,8]. Already 2 min after injection the major part of the 125 I-tissue kallikrein seemed to be bound to an inhibitor with a molecular weight of about 50 ± 70 kDa, as indicated by gel ® ltration.…”

“…It is a serineprotease [3] which releases pharmacologically highly active bradykinin from kininogen by limited proteolysis [3,4]. Tissue kallikrein is believed to be involved in both physiological processes such as blood pressure control [1] and in haemostasis [5], as well as pathophysiological processes as hypertension, diabetes, ulcerative colitis, Cushing' s disease, Alzheimer's disease, arthritis [1], asthma [6] and pancreatitis [7,8]. In vitro studies have shown different interactions between tissue kallikrein and the plasma proteinase inhibitors in human blood [9] compared with other mammals such as the pig [10].…”