An in vitro system has been developed to study N-acetyltransferase (NAT) activity using human liver slices in dynamic organ culture. Acetylation of para-aminobenzoic acid (PABA) and sulfamethazine (SMZ) in the presence of human liver slices was monitored by measuring the disappearance of the parent amine from the incubation medium using the colorimetric procedure of Bratton & Marshall. Presence of the acetyl conjugate was confirmed using HPLC. PABA acetylation rates varied from 0.72-2.52 nmoles/hr/mg protein (n = 8). This small variation (4 fold) is consistent with the classification of PABA as a monomorphic substrate. The variation in the rate of SMZ acetylation was greater than 20 fold (0.144-3.68 nmoles/hr/mg protein; n = 9). This larger variation is characteristic of SMZ as a polymorphic substrate. The results obtained indicate that human liver slices in dynamic organ culture can be used for the determination of hepatic NAT activity and acetylator status of individual human livers.

Thesis(MAppSc)--University of South Australia, 1999

Thesis (Ph. D.)--University of Queensland, 2002. / Includes bibliographical references.

No description available.

Thesis (MAppSc in Pharmacy)--University of South Australia, 1996

Thesis (Ph.D.)--University of Western Australia, 2006.

Laboratory serum biochemical tests are regarded by the Liver Study Group (LSG) of the WSAVA as an essential component of any liver investigation. The LSG categorised liver disease into four groups: vascular disorders, biliary disorders; parenchymal disorders and neoplasia. The laboratory tests that evaluate the liver have three categories. The cytosolic enzymes assess hepatocellular integrity; the cholestatic or inducible enzymes assess the biliary tree, liver excretory pathways and possible enzyme induction. The third category is the liver function tests which assess overall hepatic functional mass and portovascular integrity. The liver function tests commonly used include plasma ammonia concentration, serum bile acid concentrations and various tests that evaluate the uptake and conjugation of metabolites by the liver. Uric acid was once used as a liver test in the late 1950’s early 1960’s. Physiologically, uric acid is an attractive candidate for a liver function test. In most mammalian species serum uric acid levels only increase to the levels encountered in humans when there is hepatic dysfunction. Uric acid fell out of favour as a liver function test following the publication of two studies and one case report in the late 1950’s. The differences between hepatocellular integrity tests, cholestatic tests and tests of liver function were not fully understood at that time. The authors unfairly compared uric acid, essentially a liver function test, to a test of cholestasis. In addition the authors had very vague inclusion criteria for their liver disease cases. Despite the short-comings in these studies several prominent reference texts have since perpetuated their findings and uric acid fell out of the reckoning as a test of liver function. Many tests of liver function have been used over the years. Dynamic function tests have gained popularity again. Plasma ammonia concentration is a very reliable test of liver function but has very stringent sample-handling requirements which often make its application in the average clinic setting impractical. Serum bile acid concentrations, while not as sensitive or specific for portovascular shunting as ammonia, are widely regarded as the best test of overall liver function, especially with respect to non vascular-associated liver disease. However bile acid assays are not widely available in South Africa resulting in delays in turn-around times. In today’s climate of ever increasing costs, and demand for rapid turn around times, it would be very useful to veterinarians if a simple, rapid, cheap and robust assay could be found for evaluating functional hepatic mass. Uric acid would seem to have this potential and it is performed by most medical laboratories. In this study the serum uric acid concentrations and concentration of bile acids of a control group of normal dogs was used to compare to those in three other groups of dogs. Two of these groups had liver disease, and the third was a renal disease group. The one group of liver disease was comprised of dogs with congenital vascular anomalies while the second liver disease group was made up of dogs with various parenchymal liver diseases. Serum bile acid concentrations in the four groups were compared to the serum uric acid levels to assess the utility of uric acid as a test of liver function; and to measure the affects of diminished renal function on serum uric acid concentrations. There were significant differences in the serum bile acid concentrations between the two liver disease groups and the non-liver disease groups. Uric acid concentrations between all four groups did not differ significantly however. Serum uric acid was elevated in dogs with renal impairment. Therefore the findings in this study indicate that uric acid cannot be used as a test of liver function and is not comparable to serum bile acids in this regard. Copyright / Dissertation (MMedVet)--University of Pretoria, 2009. / Companion Animal Clinical Studies / unrestricted

No description available.

No description available.

The metabolism of lignocaine to monoethylglycinexylidide has been found useful as an indicator of hepatic function in association with liver transplantation. It has been postulated that this might be due to the common effect of hypoxic damage on liver function and lignocaine metabolism. The aim of this work was to establish whether hepatic lignocaine elimination was impaired by hypoxia and whether lignocaine extraction ratio and clearance could be used as an indicator of hepatic function. This was studied using the isolated pig liver perfused via the hepatic artery and portal vein. To establish whether the pig liver could be used as a possible human model for this investigation and whether lignocaine had any detrimental effects on liver function and blood flow in vivo, hepatic lignocaine elimination and the effects of lignocaine administration on hepatic function and blood flow were studied in the anaesthetized pig, surgically prepared to allow sampling across the liver and direct hepatic blood flow measurement. Hepatic lignocaine elimination was then studied in the isolated perfused liver to determine whether this was similar to that found in vivo. The definitive studies required preliminary investigations not available from the literature to determine the feasibility of comparing in vivo and ex vivo hepatic function using the same liver. In addition, by studying the decay of lignocaine after bolus dose administration the necessary pharmacokinetic parameters to achieve similar constant hepatic affluent lignocaine concentrations in vivo and in the isolated preparation could be determined. The preliminary investigations showed that a sequential experiment using the same liver to compare in vivo and ex vivo function was inappropriate as the energy state of isolated perfused livers previously studied in vivo was significantly different from that in livers perfused immediately. The decay of lignocaine after a bolus dose in vivo and ex vivo could be described by a two-compartment open model and in both preparations the derived pharmacokinetic parameters from this analysis were used to achieve similar constant hepatic affluent concentrations over the study period used to determine hepatic lignocaine elimination. Lignocaine extraction ratio by the in situ pig liver was similar to that reported in man and together with hepatic clearance and intrinsic clearance was similar to that determined in the isolated state when different livers were used for this comparison. There was no detrimental effect of lignocaine administration on hepatic function and blood flow In vivo. Lignocaine extraction ratio and clearance and monoethylglycinexylidide formation were significantly impaired in livers subjected to hypoxia. Lignocaine elimination correlated strongly with hepatic cellular ATP, energy charge and ATP/ ADP ratio as well as with hepatic potassium release but less strongly with aspartate aminotransferase release when this relationship was tested using the combined data from hypoxic and normoxic livers ex vivo. These correlations were positive for hepatic adenine nucleotide status and negative for hepatic potassium and aspartate aminotransferase release. Neither hepatic alanine aminotransferase release nor lactate utilization were significantly affected by hypoxia. Lignocaine extraction ratio, hepatic oxygen consumption, ATP content, bile flow and potassium release were shown to be equivalent, more highly sensitive, and earlier indicators of hypoxic hepatic injury than hepatic aspartate aminotransferase release in the isolated perfused pig liver.