Metabolic Interaction of Ethanol and Alprenolol in Isolated Liver Cells

Absrracf:The actylation of sulfanilamide and procainamide in suspensions of isolated rat parenchymal cells was studied in absence and presence of ethanol (33 mM), acetate (0.5-5 mM), citrate (4 mM), pyruvate (4 mM), and L(-)carnitine (2 mM). Ethanol treatment enhanced the sulfanilamide acetylation whereas the acetylation of procainamide was considered to be unchanged. Acetate(1-5 mM), citrate, andpyruvate treatment enhanced the acetylation of both sulfanilamide and procainamide. Acetate (4 mM) increased both K, and Vmax of both sulfanilamide and procainamide acetylation. Combined treatment with L(-)carnithe and either acetate, pyruvate, or citrate enhanced the acetylation rate of sulfanilamide more than acetate, pyruvate, or citrate, respectively alone. In cell suspensions treated with L(-)carnitine and acetate or pyruvate, the acetylation kinetics of sulfanilamide changed from zero-to apparent first-order. With procainamide as test drug, a further increase of the acetylation rate was found when L(-)carnithe was added to citrate or pyruvate. Acetyl-CoA increased the rate of sulfanilamide acetylation in rat liver homogenates in a dose dependent manner.

mentioning

confidence: 99%

Interaction between Drug Acetylation and Ethanol, Acetate, Pyruvate, Citrate, and L(minus;)Carnitine in Isolated Rat Liver Parenchymal Cells

Olsen

1982

“…also very little inhibitory effect on drug oxidation in these cells (GRUNDIN 1975). The effect of rotenone on p-nitroanisole metabolism in the isolated liver cells was not very pronounced, there was, however, a significant decrease in the amount of conjugated products with a concomitant increase in the amount of free phenol (fig.…”

Section: -0 Glucuronide5mentioning

confidence: 89%

“…1970). In isolated liver cells, on the other hand, ethanol stimulated these reactions at low concentrations ( 5 mM) but was inhibitory at higher concentrations (GRUNDIN 1975). The glucuronidation of p-nitrophenol in microsomes was inhibited to only a minor extent even at concentrations up to 100 mM.…”

Section: A-amentioning

confidence: 91%

Oxidative and Conjugative Metabolism of p–Nitroanisole and p–Nitrophenol in Isolated Rat Liver Cells

Moldéus

Vadi

Berggren

1976

Isolated rat liver cells were used in the study of p–nitroanisole and p–nitrophenol metabolism. p–Nitroanisole was o–dealkylated to form p–nitrophenol which was subsequently conjugated to form predominantly sulphate esters and β–glucuronides. 1. At low concentrations of p–nitrophenol, sulphate conjugation was predominant but with increasing substrate concentration the glucuronidation activity was increased. At 250 μM p–nitrophenol the major conjugate formed was glucuronide while sulphate conjugation was inhibited. 2. With p–nitroanisole in low concentration, resulting in low oxidation rate, all the p–nitrophenol formed was further conjugated to sulphate esters. With higher phenol production, glucuronide conjugates were also formed. 3. Phenobarbital treatment of the rats increased the rate of p–nitroanisole oxidation by more than four times but had very little effect on the conjugation reactions. In these cells the major conjugate formed was glucuronide. 4. The rate of glucuronidation in the isolated liver cells was higher than in microsomes and responded differently to various inhibitors. Alprenolol, a substrate of the hepatic mono–oxygenase system, had no inhibitory effect on glucuronidation in microsomes in the absence of NADPH. However, low concentrations of alprenolol showed similar inhibitory effects in microsomes in the presence of NADPH as in isolated liver cells. 5. Nitrophenol glucuronide was strongly inhibitory to the glucuronidation in microsomes while almost no inhibition was observed in the isolated liver cells, probably due to poor penetration of the glucuronide through the cell membrane. 6. Rotenone, menadione and ethanol had little effect in microsomes but were potent inhibitors of glucuronidation in the isolated liver cells, most probably by interfering with the synthesis of UDPGlcA. The effect of ethanol was maximal at as low a concentration as 10 mM and was shown to be due to alcohol dehydrogenase–dependent ethanol oxidation. The inhibition was presumably caused by the the increased cytoplasmic NADH/NAD4 ratio resulting from the metabolism of ethanol.

“…Interactions with drug metabolism have been studied in suspensions of purified parenchymal cells (GRUNDIN 1975;MOLDEUS et al 1976), but never in mixed cell suspensions. We decided to use primary suspensions for further studies because they were shown to metabolize antipyrine at a rate equal to purified parenchymal cells, and also because they are most easy to prepare.…”

Section: Discussionmentioning

confidence: 99%

“…and to be useful in the study of short term drug-drug metabdic interactions (VON BAHR etal. 1974;MOLDEUS et al 1976;GRUNDIN 1975;ERICSON & HOLTZMAN 1976; SCOTT HAYES & BRENDEL 1976). One major advantage provided by dilute suspensions of liver cells is that the metabolism of drugs can be studied as the only mechanism responsible for alterations in drug concentrations measured.…”

Section: Frymentioning

confidence: 99%

Metabolism of ¹⁴C‐Antipyrine in Suspensions of Isolated Rat Liver Cells

Aarbakke

Bessesen

Marland

1977

Suspensions of liver cells isolated from perfused rat livers were incubated with antipyrine‐N‐methyl‐14C. Antipyrine was eliminated by first‐order kinetics during incubations for 3 hours with primary suspensions (parenchymal cells + non‐parenchymal cells) and suspensions of purified parenchymal cells. Antipyrine concentrations were unchanged when incubated with suspensions of non‐parenchymal cells, dead cells or medium only. At the end of incubation period, 4‐OH‐antipyrine and 3‐CH2OH‐antipyrine were detected mainly as the glucuronide or sulphate conjugates, and evidence for the N‐demethylation of antipyrine was also obtained. Half‐lives for elimination of antipyrine in primary cell suspensions were not significantly different from the half‐lives measured in parenchymal cell suspensions. This finding together with the lack of metabolism of antipyrine found in non‐parenchymal cell suspensions suggest that oxidation and conjugation of antipyrine is mainly confined to the parenchymal cells. There was significant inhibition of antipyrine metabolism in primary suspensions by phenylbutazone (1.6 × 10‐3 M), dexamethasone (2 × 10‐4 M) and ethanol (1.3 × 10‐2 M, 0.75 %0). We suggest that the use of primary suspensions of isolated rat liver cells provide a rapid and simple method for the study of factors influencing drug metabolism in the liver.