Liver perfused

Zhang HX, Sultatos EG. 1991. Biotransformation of the organophosphorus insecticides parathion and methyl parathion in male and female rat livers perfused in situ. Drug Metab Dispos 19 473-477. 

Of particular interest in brevetoxin research are the diagnosis of intoxication and identification of brevetoxins and their metabolites in biological fluids. We are investigating the distribution and fate of radiolabeled PbTx-3 in rats. Three model systems were used to study the toxicokinetics and metabolism of PbTx-3 1) rats injected intravenously with a bolus dose of toxin, 2) isolated rat livers perfused with toxin, and 3) isolated rat hepatocytes exposed to the toxin in vitro. 

To further investigate the role of the liver in brevetoxin metabolism, PbTx-3 was studied in the isolated perfused rat liver model (27, 28). Radiolabeled PbTx-3 was added to the reservoir of a recirculating system and allowed to mix thoroughly with the perfusate. Steady-state conditions were reached within 20 min. At steady-state, 55-65% of the delivered PbTx-3 was metabolized and/or extracted by the liver 26% remained in the effluent perfusate. Under a constant liver perfusion rate of 4 ml/min, the measured clearance rate was 0.11 ml/min/g liver. The calculated extraction ratio of 0.55 was in excellent agreement with the in vivo data. Radioactivity in the bile accounted for 7% of the total radiolabel perfused through the liver. PbTx-3 was metabolized and eliminated into bile as parent toxin plus four more-polar metabolites (Figure 3). Preliminary results of samples stained with 4-(p-nitrobenzyl)-pyridine (29) indicated the most polar metabolite was an epoxide. 

Recently, there has been success in generating cocultures that more faithfully reproduce in vivo metastatic microenvironments. An ex vivo microscale liver perfusion bioreactor was used to assess metastatic seeding, mimicking the salient features of fluid dynamics and functionality of hepatic parenchyma. Invasion and subsequent growth of breast and prostate carcinoma cells were detected by two-photon microscopy of fluorescently labeled cells. Tumors... 

Beije, B., Onfelt, A. Olsson, U. (1984) Influence of dietary selenium on the mutagenic activity of perfusate and bile from rat liver, perfused with 1,1-dimethylhydrazine. Mutat. Res., 130, 121-126... 

Takino, T., Nagahama., E., Sakaeda, T., Yamashita, F., Takakura, Y., and Hashida, M. (1995) Pharmacokinetics disposition analysis of lipophlic drugs injected with various lipid carriers in the single-pass rat liver perfusion systerrlnt. J. Pharm., 114 43-54. 

Table 19.1 Moments and disposition parameters of 32P-pDNA and 32P-oligonucleotides in the single-pass rat liver perfusion system...

Figure 19.5 Physiological pharmacokinetic model for hepatic uptake of drug constantly infused in the isolated rat liver perfusion system. Q, flow rate (mL/min) Cb, inflow concentration (pg/mL) Cs, sinusoidal concentration (pg/mL) Vs, sinusoidal volume (mL) X, binding constant (pg) Xm, maximum binding amount (pg) K, binding constant (mL/pg) kmt, internalization rate constant (min-1).

Takakura, Y., Mahato, R.I., Yoshida, M., Kanamaru, T. and Hashida, M. (1996) Uptake characteristics of oligonucleotides in the isolated rat liver perfusion system. Antisense Nucleic Acid Drug Develop., 6,177-183. 

IRES, Internal ribosomal entry site, 8 Isolated liver perfusion, 419... 

Some efforts have been made to determine the effect P-gp has on its substrates by use of in situ perfusion methods, including intestinal perfusion, liver perfusion, kidney perfusion, and brain perfusion. These experiments allow the researcher to study the transport of compounds in a physiologically relevant environment in which the integrity of the organ is preserved with regards to cell polarity and representation of all cell types seen in the organ. Furthermore, the reduction in complexity of in situ models versus in vivo studies facilitates the conduct of complex studies and allows more definitive conclusions to be made regarding the role P-gp may play in disposition. 

A2. Abbey, M., Savage, J. K., Macldnnon, A. M., Barter, P. J., and Calvert, G. D., Detection of lipid transfer protein activity in rabbit liver perfusate. Biochim. Biophys. Acta 793, 481-484 (1984). 

Distribution of the radioactivity (a) after a 24-h experiment on living animals (oral ingestion) and (b) after a 2-h liver perfusion (28). 

Bartosek, I. Guaitani, A. Garattini, S. In "Isolated Liver Perfusion and... 

Figure 3 shows the results of the electrophoretic separation of a specimen of plasma taken from an eviscerated surviving rat 4 hours after an infusion of 320 microciiries of S3504 given as carrier-free inorganic sulfate and analogous to the dose used in the isolated liver perfusion of Figure 1. The lower half of Figure 3 reveals that the amounts of S35 present in the seromucoid fractions of the plasma from the evis-...

Figure 4. Electrophoretic separation of plasma protein from isolated rat liver perfusion with acetate-1-C1 ...

Figure 9. Results of simultaneous preparative electrophoresis of equal samples (0.5 ml.) of plasma obtained from blood taken 0, 2, and 5 hours after start of liver perfusion (Figure 8)...

Fibrinogen Biosynthesis by Isolated Liver. In our isolated rat liver perfusion studies homologous heparinized oxygenated rat blood is routinely diluted with Ringer s solution, so that its final volume is in-... 

The results of Figure 11 are in striking contrast. Here, when the liver perfusion is carried out with completely defibrinated blood, there is a remarkable net synthesis of fibrinogen which becomes prominent only after the second to third hour and is impressive by the fifth and sixth hours. The chemically measured circulating level of fibrinogen has increased some 60 mg. % above that present in the zero time specimens. Net synthesis of fibrinogen of this magnitude has been repeatedly obtained in more than 25 perfusion studies which will be detailed elsewhere. 

It is of some interest to inquire whether one may affect the net synthesis of fibrinogen under conditions of extreme hypofibrinogenemia associated with maximal fibrinogen production. Table I reveals that the amino acid analog L-ethionine, 5.6 mg. at the outset of liver perfusion, followed by continuous infusion of 3 mg. per hour after an initial priming dose, greatly suppresses the biosynthesis of fibrinogen. 

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