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T Garzó

Publications and source records attributed to T Garzó.

At least 37 records · Page 2Linked to original sources
PubMed1989

Changes of prostacyclin and thromboxane synthesis in the course of mouse liver perfusion. Stimulated thromboxane A2 synthesis of freshly prepared isolated mouse hepatocytes.

The formation of prostacyclin and thromboxane A2 (measured as 6-keto PGF1 alpha and TXB2 by radioimmunoassay) was investigated during a 30 min perfusion of mouse liver in a recirculation system. After cannulation of the portal vein an immediate increase of de novo synthesis and secretion of PGI2 occurred followed by a sharp decrease. Increased PGI2 synthesis was also followed by a continuous increase of TXA2 synthesis and secretion reaching a maximum at the end of the 30 min perfusion. Elevated TXA2 synthesis was also shown in freshly isolated hepatocytes investigated in the course of a 20 min incubation period immediately after the perfusion. However, the elevated TXA2 formation was not observed when it was measured after a 120 min preincubation of the cells. Both PGI2 and TXA2 production could be provoked to a similar extent by the addition of arachidonate and A 23187 immediately after the perfusion or after a 120 min preincubation.

6-Ketoprostaglandin F1 alpha↗
PubMed1989

Ethanol treatment inhibits the development of diethylnitrosamine-induced tumors in rats.

Effect of ethanol (20% in drinking water) or acetone (1% in drinking water) treatment was investigated on N-diethylnitrosamine (DEN), acetyl-aminofluorene (AAF) and partial hepatectomy (PH) induced hepatic tumors in rats. Simultaneously with the morphological detection of foci and nodules in the liver of the sacrificed rats, the activities of isozymes of cytochrome P450IIE gene subfamily responsible for the oxidation of ethanol or acetone (as aniline hydroxylase) and also the activity of aminopyrine N-demethylase were determined. Nodules could be detected after DEN, AAF and PH treatment with and without combination with acetone, however nodules did not developed in ethanol treated animals even 6 months after the DEN injection. As expected acetone or ethanol selectively increased the activity of aniline hydroxylase without a general induction of P-450 enzymes. It is suggested that the induction of P-450IIE isoenzymes per se is not connected to the preventive effect of ethanol on DEN induced carcinogenesis.

Animals↗
PubMed1988

Glycogenolysis--and not gluconeogenesis--is the source of UDP-glucuronic acid for glucuronidation.

Differences in cofactor (NADPH and UDP-glucuronic acid) supply for various processes of biotransformation were studied by investigating the interrelations between glucose production (gluconeogenesis and glycogenolysis) and drug (p-nitrophenol, aminopyrine, phenolphthalein) biotransformation (hydroxylation and conjugation) in isolated murine hepatocytes. In glycogen-depleted hepatocytes prepared from animals fasted for 48 h (i) p-nitrophenol conjugation was decreased by 80% compared to the fed control, while aminopyrine oxidation was unaltered, (ii) addition of glucose or gluconeogenic substrates failed to increase the rate of p-nitrophenol conjugation, while the rate of p-nitrophenol and also aminopyrine oxidation was increased and (iii) gluconeogenesis was inhibited by 80% by aminopyrine oxidation: it was moderately decreased by p-nitrophenol oxidation and conjugation and remained unchanged by phenolphthalein conjugation. In hepatocytes prepared from fed mice (i) p-nitrophenol conjugation was independent of the extracellular glucose concentration, (ii) it was linked to the consumption of glycogen--addition of fructose inhibited p-nitrophenol glucuronidation only, while sulfation was unaltered and (iii) p-nitrophenol oxidation was not detectable: aminopyrine oxidation was not affected by fructose addition. It is suggested that UDP-glucuronic acid for glucuronidation derives predominantly from glycogen, while the NADPH generation for mixed function oxidation is linked to glucose uptake and/or gluconeogenesis in the liver.

Aminopyrine↗
PubMed1988

Accumulation of phenols and catechols in isolated mouse hepatocytes in starvation or after pretreatment with acetone.

Conditions leading to the accumulation of unconjugated phenols and catechols were investigated in mouse livers. The formation of unconjugated hydroxylated products of added p-nitrophenol and aniline was investigated in isolated hepatocytes prepared from 48 hr fasted or fed mice or from fed mice after acetone pretreatment. 4-Nitrocatechol and p-aminophenol--the hydroxylated products of p-nitrophenol and aniline--were accumulated in cells prepared from fasting animals, while in cells prepared from fed mice these unconjugated derivatives were not detectable. The accumulation of 4-nitrocatechol and p-aminophenol was also shown in isolated hepatocytes prepared from acetone pretreated fed mice. Inhibition of glucuronidation by N6,O2-dibutyryl cAMP or by D-galactosamine increased the accumulation of 4-nitrocatechol upon addition of p-nitrophenol in cells prepared from fasted mice. Both 48 hr starvation and acetone pretreatment enhanced the activity of microsomal p-nitrophenol and aniline hydroxylase by 300% and 600%, respectively, whereas p-nitrophenol conjugation in isolated hepatocytes as well as in hepatocyte homogenates was decreased by about 80% after 48 hr starvation. Acetone pretreatment did not alter the rate of p-nitrophenol conjugation measured in liver homogenates. It is suggested that a shift from conjugation toward hydroxylation in starvation gives rise to the formation of hazardous metabolites.

Acetone↗
PubMed1988

Cyclic AMP-dependent phosphorylation in the control of biotransformation in the liver.

The possibility of a short-term cAMP-dependent regulation of mixed-function oxidation and of glucuronide formation was investigated in isolated mouse hepatocytes and in mouse liver microsomal membranes. N6, O2-dibutyryl cAMP (in accordance with its increasing effect on gluconeogenesis) decreased aminopyrine oxidation and p-nitrophenol conjugation in isolated hepatocytes, while the phenolphthalein conjugation remained unaltered. Similar to dibutyryl cAMP the Ca2+ ionophore A 23187 also decreased aminopyrine oxidation. In cell-free systems the phosphorylation of isolated microsomal membranes by the exogenous cAMP-dependent protein kinase was inhibitory on aminopyrine oxidation and p-nitrophenol glucuronide formation but aniline oxidation and phenolphthalein glucuronidation were not affected. The correlation between the negative cAMP-dependent control of certain processes of biotransformation and the positive cAMP-dependent regulation of gluconeogenesis is discussed.

Aminopyrine↗
PubMed1988

Interrelationship between drug oxidation ureogenesis and gluconeogenesis in isolated hepatocytes.

1. The effect of increased ureogenesis--provoked by NH4Cl and ornithine--on gluconeogenesis and aminopyrine oxidation was studied in isolated hepatocytes prepared from 24 hr starved mice; lactate or fructose was used as gluconeogenic precursor. 2. Increased ureogenesis caused about 40% inhibition both on aminopyrine oxidation and gluconeogenesis when lactate was added as gluconeogenic substrate. 3. On the other hand, only 10% inhibition of aminopyrine oxidation and about 15% inhibition of gluconeogenesis were observed when fructose was used as gluconeogenic precursor. 4. Aminopyrine has been reported to inhibit gluconeogenesis from fructose by 30% and from lactate by 85%. The inhibitory effect of the combined addition of aminopyrine, NH4Cl and ornithine on gluconeogenesis was also dependent on the applied gluconeogenic precursor. 5. The provoked ureogenesis by ammonia and ornithine was not inhibited by aminopyrine. N6, O2-dibutyryl cAMP known to cause an increase of gluconeogenesis a decrease of aminopyrine oxidation enhanced the inhibitory action of increased ureogenesis on aminopyrine oxidation and on gluconeogenesis further. 6. The role of NADPH in the regulation of drug oxidation and ureogenesis is underlined.

Aminopyrine↗
PubMed1988

cAMP dependent inhibition of thromboxane A2, prostacyclin and PGF2 alpha synthesis in mouse hepatocytes.

The role of cAMP dependent regulation in thromboxane A2, prostacyclin and PGF2 alpha synthesis (measured by radioimmunoassay) was investigated in isolated mouse hepatocytes and in microsomal membranes prepared from these cells. In isolated hepatocytes N6,O2-dibutyryl cAMP inhibited the formation of all the three derivatives, while calcium ionophore A 23187 stimulated their synthesis. Addition of the dissociated catalytic subunit of cAMP dependent protein kinase and ATP to microsomal membranes inhibited the production of TXA2, PGI2 and PGF2 alpha by about 50% and this inhibition was counteracted by the combined addition of heat stable inhibitor protein of cAMP dependent protein kinase. It is concluded that in parenchymal liver cells cAMP dependent phosphorylation is directly involved in the inhibition of prostanoid synthesis.

Animals↗
PubMed1987

Interrelationship between aminopyrine oxidation and gluconeogenesis in hepatocytes prepared from fructose-pretreated mice.

Aminopyrine oxidation was studied in isolated hepatocytes prepared from 24-h-starved mice (i) after induction of the NADPH-generating malic enzyme and glucose-6-phosphate dehydrogenase, but not the mixed function oxygenases by fructose, (ii) after induction of both mixed function oxygenases and NADPH-generating malic enzyme and glucose-6-phosphate dehydrogenase by phenobarbital and (iii) without any pretreatment. Phenobarbital pretreatment, as expected, increased the rate of aminopyrine oxidation of isolated hepatocytes. However, fructose pretreatment also enhanced the rate of N-demethylation of aminopyrine by more than 100% supporting the view that the availability of NADPH is rate limiting in drug oxidation under certain conditions. The role of malic enzyme and glucose-6-phosphate dehydrogenase in the NADPH supply for aminopyrine oxidation was investigated by the addition of two groups of gluconeogenic precursors: lactate or alanine and glycerol or fructose with the simultaneous measurement of glucose synthesis and aminopyrine N-demethylation. There was a clear correlation between the increased rate of aminopyrine oxidation and the decreases of glucose production caused by aminopyrine. Gluconeogenesis in the presence of 1 mM aminopyrine was decreased by 70-80% when alanine or lactate were used as precursors, it was decreased by only 35-40% when glucose production was started from glycerol or fructose; in an accordance with the facts that NADPH generation and gluconeogenesis starting from alanine or lactate share two common intermediates--malate and glucose-6 phosphate--, while there is only one common intermediate--glucose-6 phosphate--if fructose or glycerol are used. Similar results were obtained with the addition of the structurally dissimilar hexobarbital. It is concluded that besides malic enzyme, glucose-6-phosphate dehydrogenase also takes part in NADPH supply for drug oxidation in glycogen-depleted hepatocytes.

Aminopyrine↗
PubMed1987

Prostanoid synthesis in isolated parenchymal and nonparenchymal mouse liver cells in the presence of arachidonic acid.

Prostanoid synthesis was investigated in suspensions of isolated mouse hepatocytes and nonparenchymal liver cells. A stable metabolite of thromboxane A2 (TXB2) of prostacyclin (6-keto PGF1 alpha) and one of the prostaglandins (PGF2 alpha) was detected by radio-immuno-assay (RIA). Hepatocytes synthesized mainly TXB2, while smaller amounts of 6-keto PGF1 alpha and PGF2 alpha were detected during 60 min incubation. Homogenization of hepatocytes caused a slight increase of TXB2 production and provoked the synthesis of PGF2 alpha and 6-keto PGF1 alpha. The addition of arachidonate to hepatocytes did not influence prostanoid production at concentrations below 10-5M. Higher concentrations further increased TXB2 production and also increased the synthesis of 6-keto PGF1 alpha and PGF2 alpha. Nonparenchymal cells synthesized all the three types of prostanoids and homogenization of these cells did not result in a marked change. The addition of 10(-7)-10(-5)M arachidonate increased the TXB2, 6-keto PGF1 alpha and PGF2 alpha synthesis in nonparenchymal cells. No further increase was found at higher concentrations.

Animals↗
PubMed1987

Inhibitory effect of A 23187 on protein synthesis in isolated murine hepatocytes.

The effect of the Ca ionophore A 23187 on amino acid incorporation into protein, on gluconeogenesis and on synthesis of some eicosanoids was investigated in isolated mouse hepatocytes (i) in the presence of 2.5 mM Ca2+, (ii) in the absence of Ca2+ and in the presence of 0.2 mM EGTA, (iii) after calcium depletion. A 23187 inhibited amino acid incorporation into protein both in the presence and in the absence of Ca2+ in a concentration dependent manner, whereas in the absence of Ca2+ the known stimulating effects of A 23187 on eicosanoid synthesis could not be detected. In hepatocytes prepared from 24 h starved mice A 23187 increased the rate of gluconeogenesis and similarly to eicosanoid synthesis this stimulation in the absence of Ca2+ could not be observed. On the other hand, after calcium depletion the inhibition of protein synthesis by A 23187 was markedly moderated. It is concluded that the effect of A 23187 on protein synthesis is also related to its ionophoretic effect but calcium sensitivity in this effect is smaller than in gluconeogenesis or eicosanoid synthesis.

Animals↗
PubMed1985

Association of alpha 2-macroglobulin-thrombin and alpha 2-macroglobulin-plasmin complexes with isolated hepatocytes.

125I-labelled alpha 2-macroglobulin complexed with thrombin or plasmin bound to hepatocytes in a concentration- and time-dependent manner. The apparent Kd values calculated from displacement experiments were 7.9 X 10(-8) M for alpha 2-macroglobulin-thrombin and 8.5 X 10(-8) M for alpha 2-macroglobulin-plasmin. Association of these complexes was only partially reversible; after a 180 min incubation period, 50-60% of the bound radioactivity was internalized by the cells. alpha 2-Macroglobulin itself bound also to hepatocytes, but the affinity of the alpha 2-macroglobulin complexes was higher than that of the inhibitor alone, and alpha 2-macroglobulin was not internalized, either. 125I-labelled thrombin or plasmin bound to hepatocytes as well. These bindings were also concentration-dependent and could be decreased with an excess of unlabelled ligands. Binding rates and amounts of the bound proteinases were higher than those of their alpha 2-macroglobulin complexes. The alpha 2-macroglobulin-thrombin complex competed with the alpha 2-macroglobulin-plasmin complex in binding to hepatocytes, whereas there was no competition between these complexes and the antithrombin III-thrombin complex. These results suggest that the binding sites of hepatocytes for alpha 2-macroglobulin-proteinase and antithrombin III-proteinase complexes are different.

Animals↗
PubMed1984

Uptake of arachidonic acid, arachidic acid, oleic acid and their incorporation into phospholipids and triacylglycerols of isolated murine hepatocytes. Effect of thrombin-antithrombin III complex.

Uptake and metabolism of arachidonic acid, arachidic acid and oleic acid were investigated in isolated hepatocytes prepared from mouse liver with the collagenase perfusion method. The rate of uptake of arachidonic acid was time- and concentration- dependent. 94-98% of the arachidonic acid was incorporated into the phospholipid and triacylglycerol fractions following a 60 min incubation period at 37 degrees C. In the presence of thrombin-anti-thrombin III complex a change in the distribution of arachidonic acid incorporated into lipid fractions was found, i.e. increased incorporation into phosphatidyl-serine and phosphatidylethanolamine, whereas the uptake was not altered. There was no change in the uptake and incorporation of arachidic acid and oleic acid.

Animals↗
PubMed1984

Prostaglandin and thromboxane synthesizing activity in isolated murine hepatocytes and nonparenchymal liver cells.

Prostanoid synthesis from 3H-arachidonic acid was compared in isolated parenchymal and nonparenchymal murine liver cells. The cells incorporated arachidonic acid into phospholipids but no prostanoid synthesis could be measured during 30 min incubation. Conditions necessary for prostanoid synthesis were different in parenchymal and nonparenchymal cells and the products were also different. Prostanoid synthesis could be induced by in vitro partial hepatectomy: parenchymal cells synthesized thromboxane A2 whereas nonparenchymal cells produced prostaglandin E2 and F2 alpha. Prostaglandin E2 and F2 alpha synthesis could be provoked also by homogenization of the nonparenchymal cells prepared from normal liver, while the homogenates of parenchymal cells prepared from normal liver did not synthesize thromboxane. Imidazole and indomethacin inhibited the production of thromboxane and prostaglandins, respectively. Our results suggest that the various cell types of the liver respond by the synthesis of different and specific prostanoids after the same injury.

Animals↗
PubMed1982

Reversible inhibition of RNA synthesis and irreversible inhibition of protein synthesis by D-galactosamine in isolated mouse hepatocytes.

The inhibition of RNA synthesis of isolated mouse liver parenchymal cells caused by 10 mM D-galactosamine was reversible, while the inhibition of protein synthesis remained unaltered after the removal of galactosamine. 10(-5)M epinephrine and 10(07)M glucagon have been shown to decrease aminoglycogen formation and thus to reduce the inhibitory effect of galactosamine on protein synthesis (II). However, these hormones did not decrease the inhibition of RNA synthesis. 10 mM D-galactosamine did not effect the nucleoside and amino acid incorporation of isolated non-parenchymal mouse liver cells. The predominant role of aminoglycogen in the inhibition of protein synthesis in galactosamine induced liver injury is discussed.

Animals↗
PubMed1979

Epinephrine and glucagon counteract inhibition of protein synthesis induced by D-galactosamine in isolated mouse hepatocytes.

10 mM D-galactosamine enhibited protein synthesis (1 h incubation time) by 67% in isolated mouse liver cells. Counteracting uridylate deficiency induced by D-galactosamine by preventive administration of 20 mM uridine did not decrease the extent of protein synthesis inhibition. 20 mM D-galactose reverted the inhibition of protein synthesis by D-galactosamine. 10(-5) M epinephrine and 10(-7) M glucagon decreased the incorporation of D-galactosamine into glycogen to 38% and 26% of the control value, respectively, after a 35 min incubation and reduced the inhibition of protein synthesis by D-galactosamine effectively. Experimental evidence supports the view that aminoglycogen formed after D-galactosamine treatment is responsible for the inhibition of protein synthesis.

Amino Sugars↗
PubMed1977

Cytoplasmic aggregates in D-galactosamine induced liver injury.

D-galactosamine treatment leads to the formation of PAS-positive granules or aggregates in the cytoplasm of mouse liver cells. Ultrastructural observations show that the granules consist of particles surrounded by membranes of rough endoplasmic reticulum. Cytochemical results reveal that part of the particles is pronase-sensitive and amylase resistant, staining positively by the Thiéry silver proteinate method. The other part is stained positively by EDTA preferentional staining. According to the cyto-and histochemical results the granules consist of ribosomes and abnormal basic glycogen. The aggregates are removed from the cytoplasm mostly by lysosomal degradation.

Animals↗