Turnover of Plasma Kininogens in Rhesus Monkeys

Abstract

Radiolabelled purified plasma kininogens were injected into healthy rhesus monkeys for the purpose of studying their normal metabolic turnover. Human kininogen was purified using affinity chromatography and further fractionated into high molecular weight (HMW) and low molecular weight (LMW) proteins as described by Pierce and Guimaraes (Fogarty International Center Proceedings No. 27, pp. 113-119, 1976). The kininogens were labelled with 125I using either the choramine-T or microdiffusion techniques. Labelled mixed kininogen, LMW kininogen, and HMW kininogen preparations were injected into 6, 4, and 6 rhesus monkeys respectively. Blood samples were drawn at various time intervals, and assayed in a gamma counter. The disappearance of injected labelled kininogen from the intravascular compartment could be expressed as a double exponential equation. The difference between the half-life of HMW kininogen (26.0 ± 1.6 h) (± SE) and that of LMW kininogen (20.2 ± 2.1 h) was only marginal (P >0.05). In contrast there was a highly significant (P < 0.001) difference in their fractional catabolic rates (1.12 ± 0.09 day-1 for HMW kininogen and 2.05 ± 0.12 day-1 for LMW kininogen). These observations indicate that although there is a minimal difference in the metabolic rates of intravascular HMW and LMW kininogens, a considerable difference exists in their rates of flux between the intravascular and extravascular spaces.