María Morales

Effect of pyrazole on rat liver catalase

Abstract Pyrazole alone does not affect catalase activity in vitro; however, its administration in vivo produces irreversible inhibition of catalase in rat liver and kidney but not in blood. The inhibition in the liver, after a 70 mg/kg single dose of pyrazole, follows first-order kinetics with a half-life of 8 hr. The activity reaches a minimum at 28 hr followed by gradual recovery at a rate corresponding to a half-life of 1.19 days. This value agrees with previous half-life determinations for rat liver catalase; therefore it is taken as evidence that the irreversibility of the inhibition demonstrated in vitro is also maintained in vivo. The inhibition of catalase is mediated by a product from the metabolism of pyrazole by the microsomal mixed-function oxidase system. This active pyrazole derivative presumably reacts with catalase hydrogen peroxide complex I, and not with the native catalase, in a process that can be prevented by alcohol. It is shown that pyrazole, a drug also used as an alcohol dehydrogenase inhibitor, is eliminated from the liver in a simple exponential process with a half-life of 3.45 hr, which agrees with its reported effects on ethanol metabolism in vivo.

Thrombin Generation in Platelet-Poor Plasma Is Normal in Patients with Hereditary Mucocutaneous Haemorrhages

Mild hereditary bleeding disorders presenting with mucocutaneous haemorrhages are usually difficult to diagnose. We measured thrombin generation in platelet-poor plasma (TG-PPP) in 206 patients with a clinically unequivocal bleeding tendency: 45 with von Willebrand disease (vWD), 49 with platelet aggregation/secretion defects (PASD), 10 with a combination of both and 102 who did not fit the diagnostic criteria for any known haemostatic disorder. TG-PPP was not significantly different from controls in all patient groups, indicating that an abnormality in the plasmatic clotting system is unlikely to contribute to the bleeding in patients with type 1 vWD and PASD. In patients with undiagnosed mild hereditary bleeding disorders, there must be other mechanisms which explain the abnormal haemorrhagic tendency, most likely as yet unrecognized defects in platelet-vessel wall interaction. As a next step we plan to investigate thrombin generation in PRP.

Platelet membrane glycoprotein polymorphisms do not influence the clinical expressivity of von Willebrand disease type 1

Von Willebrand disease (VWD) is characterized by a significant variation in bleeding symptoms among patients with similar laboratory profiles and equivalent plasma levels of von Willebrand factor (VWF) activities. Considering the recent suggestion that platelet membrane glycoprotein polymorphisms (PltGPs) may play a role as modulators of thromboembolic or haemorrhagic diseases, we investigated the role of different PltGPs and GPVI content in the clinical expression of patients with VWD type 1.The diagnosis of VWD (n = 76) was based on laboratory findings (VWF:Ag, VWF:RCo, VWF:CB, FVIII:C, and multimer analysis), family and personal history of bleeding. All patients were interviewed using a standardized questionnaire, and classified into two categories: bleeders (unequivocal bleeding tendency, n = 53) and non bleeders (absence of bleeding symptoms, n = 23). PltGPs, HPA-1, 2 and 5 and C807T of GPIa were determined by fluorophore-labelled hybridization probes on a LightCycler. GPVI content was measured by western blotting. VWF:Ag,VWF:RCo,VWF:CB and FVIII:C levels were not significantly different between symptomatic and asymptomatic patients. There were no differences in the genotype distribution and allele frequencies between bleeders and non bleeders for the platelet alloantigen systems HPA-1, 2, 5 and the GPIa C807T polymorphism. The levels of platelet GPVI were similar in symptomatic and asymptomatic VWD patients (109.6 +/- 58.4 vs 114.1 +/- 52.5, respectively; p: 0.77). These results show that PltGPs HPA-1, 2 and 5 or the C807T dimorphism of GPIa do not influence the clinical expressivity of VWD type 1. The wide variation in GPVI content was not associated with the severity of bleeding in the patients. Other genetic factors that may contribute to the variable expressivity of VWD type 1 should be investigated.

Induction of peroxisomal fatty acyl-coenzyme A oxidase and total carnitine acetyl-coenzyme A transferase in primary cultures of rat hepatocytes by garlic extracts

Garlic has been proposed as a natural hypolipidemic substance. Most hypolipidemic compounds induce peroxisomal proliferation and increase enzyme activities associated with peroxisomal beta-oxidation in rat liver. Here we report that garlic methanol-extracts behave as hypolipidemic drugs, increasing the activity of peroxisomal fatty acyl-coenzyme A oxidase and of total carnitine acetyl-coenzyme A transferase in primary cultures of rat hepatocytes. Both enzymes are considered markers associated with increased peroxisomal beta-oxidation. As in the case of hypolipidemic peroxisome proliferators, garlic extracts partially prevented the decrease in fatty acyl-coenzyme A oxidase as the culture aged. No changes were observed in the activity of microsomal NADPH cytochrome c reductase or of mitochondrial glutamate dehydrogenase.