Search

Rats and mice were fed a diet containing aspirin at levels of 0, 0.3, 0.6 and 1.2% for 1 and 4 weeks. Haemorrhagic death and/or haemorrhagic anaemia occurred in rats in a dose-dependent manner. Prothrombin and kaolin-activated partial thromboplastin time indices were also decreased depending on the daily doses. However, no conspicuous haemorrhagic signs were found in mice given aspirin. These results suggest marked differences in haemorrhagic effects of aspirin between rats and mice. From results of supplementary experiments with two metabolites of aspirin, salicylic acid and gentisic acid, and from the fact of close relationship between hepatic concentration of salicylic acid and haemorrhagic effects of aspirin, it is inferred that salicylic acid may be a precursor for the active metabolite(s) to cause haemorrhage. The mechanism of species differences of aspirin is discussed.

Factor XII has been assayed as kaolin-activated prekallikrein activator in rat citrated plasma pretreated with acetone (Briseid et al. 1978 & 1979; Briseid & Berstad 1979). In the present work benzamidine added during blood collection increased the extent of activation by a factor of 6. Rat high molecular weight kininogen (HMWK) added to acetone-treated citrated plasma likewise increased the activation, providing evidence of the protection by benzamidine of the cofactor function of HMWK. All cofactor capacity was retained after the removal of the kinin part of HMWK. Experiments carried out with plasminogen-free plasma showed that plasmin could hardly be the the factor responsible for the destruction of HMWK. The stoichiometric factor XII concentration-effect curve obtained by diluting acetone-treated rat plasma with acetone-treated human factor XII deficient plasma showed that factor XII is present in functional excess, the concentration of HMWK deciding the extent of activation. By diluting acetone-treated rat plasma with buffer, HMWK concentration-effect curves were obtained which were approximately linear over a range of 0.03-0.40 microgram (bradykinin equivalents) per ml kaolin incubate. No further activation of factor XII was obtained at 0.80 microgram/ml.

Activation of plasminogen-free rat citrated plasma (RCPL-P) with acetone/kaolin yielded BAEe-esterase activities of 0.6--0.8 U/ml. Gel filtration demonstrated one single peak of BAEe-esterase activity (mol. wt. approximately 135000) with a kininogenase-esterase ratio (3.3) close to that known for human plasma kallikrein (2.7). Similarly activated rat citrated plasma (RCPL) revealed on gel filtration an additional esterase peak (mol. wt, approximately 47,000) with a low kininogenase-esterase ratio (0.3), and should accordingly not be used for a BAEe-esterase assay of rat plasma kallikrein. Acetone activation of RCPL-P and of RCPL yielded prekallikrein activator (PKA) activities which were about doubled by treatment with kaolin to 1.9--2.1 and 3.5--4.2 PKA-U/ml respectively. Gel filtration of acetone-activated RCPL-P or RCPL revealed two peaks of PKA activity, mol. wt. approximately 110,000 corresponding to activated factor XII (XIIa), and mol. wt. approximately 33,000 corresponding to XII fragments (XIIf). Kaolin-treatment of acetone-activated RCPL-P, but not of RCPL, caused an extensive fragmentation of XIIa to the 4--6 times more active XIIf. The lower yield of PKA-activity in acetone/kaolin-activated RCPL-P, as compared with activated RCPL, seems to be due to the absence of a factor of significance for the activation of factor XII, which is not plasmin, plasma kallikrein, or high molecular weight kininogen.

It was previously observed that serotonin injected intravenously into the rat caused significant reductions in the prekallikrein activator (PKA) and the benzoyl arginine ethyl ester (BAEe)-esterase activities induced in rat plasma by acetone/kaolin activation. In the present work it was demonstrated that serotonin was unable to exert these effects in vitro, in plasma or in whole blood. The assay of PKA and Baee-esterase activities after gel filtration on Sephadex G-100 of acetone-activated plasma from rats treated with serotonin 0.10 mg/kg revealed reduced fragmentation of factor XII, and reduced levels of kallikrein and of an additional BAEe-esterase. Serotonin also lowered the plasminogen level. The serotonin-induced reductions of PKA and BAEe-esterase were inhibited by pretreatment of the rats with epsilon-aminocaproic acid. Evidence was provided that serotonin did not lower the plasma level of factor XII of the coagulation system, but the level of a factor of significance for the activation of factor XII. All the above-mentioned serotonin effects were fundamentally similar to the corresponding effects caused by dextran. It is concluded that the effects of dextran on the plasma parameters mentioned are mediated by the release of endogenous serotonin.

Sera from 341 individuals living in the distribution area of the tick Ixodes recinus were tested for tick-borne encephalitis (TBE) antibodies by HAI and gel diffusion. Kaolin treatment was unreliable for the removal of non-specific HAI inhibitors. Seven sera positive after this treatment were shown to be negative after acetone extraction/flotation centrifugation. The antibody prevalence rate was 19.6%. Seventy-one % of the sera had titres greater than or equal to 40. The prevalence rate decreased with age. Some sera with low HAI titres could be confirmed by a sensitive Ouchterlony technique, while some with high titres could not, even after ten-fold concentration. Clinical information obtained retrospectively regarding patients with high antibody titres revealed some cases consistent with a TBE virus infection. Antibody prevalence rates indicate that TBE virus is more active than Uukuniemi and Kemorovo group virus in tick-infested areas. Mixed foci of these viruses have been indicated by serological findings and virus isolations.