Biomedical subjects

P Olinga

Publications and source records attributed to P Olinga.

26 records · Page 2Linked to original sources

PubMed1998

In vitro and in vivo metabolism of the progestagen Org 30659 in several species.

The metabolism of Org 30659 [(17alpha)-17-hydroxy-11-methylene-19-norpregna-4, 15-dien-20-yn-3-one], a new potent progestagen currently under clinical development by NV Organon for use in oral contraceptive and hormone replacement therapy, was studied in vivo after oral administration to rats and monkeys and in vitro using rat, rabbit, monkey, and human liver microsomes and rat and human hepatocytes. After oral administration of [7-3H]Org 30659 to rats and monkeys, Org 30659 was extensively metabolized in both species. Fecal excretion appeared to be the main route of elimination. In rats, opening of the A-ring, resulting in a 2-OH,4-carboxylic acid, 5alpha-H metabolite of Org 30659, was the major metabolic route in vivo. Other metabolic routes involved the introduction of an OH group at C15beta, followed by a shift of the Delta15-double bond to a 16/17-double bond with subsequent removal of the OH group at C17 and reduction of the 3-keto,Delta4 moiety followed by sulfate conjugation of the 3-OH substituent. These metabolic routes observed in vivo were also major routes in incubations with rat hepatocytes. In rat liver microsomes, Org 30659 was metabolized by reduction of the 3-keto,Delta4 moiety. Rat hepatocyte incubations with Org 30659 were more representative of the in vivo metabolism of Org 30659, compared with rat microsomal incubations. Both in vitro and in vivo, the majority of the metabolites were 3alpha-OH,4,5alpha-dihydro derivatives. In monkeys, Org 30659 was mainly metabolized at the C3- and C17-positions in vivo. The 3-keto moiety was reduced to both 3beta-OH and 3alpha-OH substituents. In addition to phase I metabolites, glucuronic acid conjugates were observed in vivo. In monkey liver microsomes, the 6beta-OH metabolite of Org 30659 was the major metabolite present. Similar to the monkey liver microsomes, rabbit and human liver microsomes converted Org 30659 to the 6beta-OH metabolite. This metabolite was also the major metabolite in incubations with human hepatocytes.

Animals↗

PubMed1997

Value of the in vitro or in vivo monoethylglycinexylidide test for predicting liver graft function.

BACKGROUND: An adequate function test for donor livers is still lacking. The monoethylglycinexylidide (MEGX) test, performed in vivo in the donor to measure the metabolic rate of lidocaine conversion to MEGX, has been proposed as a function test for donor livers to predict postoperative organ function. METHODS: In the present study, we investigated whether the MEGX formation rate measured in needle biopsy specimens in vitro correlates with the rate of MEGX formation in vivo. The in vivo MEGX test was performed in the donors and in the recipients on days 1 and 2. The in vivo and in vitro MEGX tests were compared with posttransplant liver function in the recipients in order to investigate their possible relevance as predictors of graft function. RESULTS: The MEGX formation rate in needle biopsy specimens in vitro showed a significant correlation with the MEGX serum concentration found in the donor. A low rate of MEGX formation in the biopsy specimens tended to predict initial poor function of the grafts. In the donor, the MEGX test did not correlate with general liver function after transplantation. Only the MEGX serum concentration in the recipients on day 2 gave an indication of graft function. CONCLUSIONS: MEGX formation in liver biopsy specimens in vitro properly reflects metabolic function of the particular liver. Therefore, liver biopsies may be a valuable tool to help predict liver function in vivo. However, the MEGX test alone is not sufficient to provide the gold standard to determine liver function in donor and transplantation livers.

Adenosine↗

PubMed1997

Influence of 48 hours of cold storage in University of Wisconsin organ preservation solution on metabolic capacity of rat hepatocytes.

BACKGROUND/AIMS: Suspensions of isolated hepatocytes are a valuable tool to study liver functions. For optimal use of the isolated hepatocytes, methods are needed to preserve the hepatocytes while maintaining their viability, metabolic and transport functions. Until now, little has been known about the maintenance of the drug metabolism capacity and energy state, measured by the so-called energy charge (ATP+1/2ADP)/(ATP+ADP+AMP), in hepatocytes after storage in University of Wisconsin cold storage solution (UW). Consequently, we investigated whether UW, originally designed to preserve organs for transplantation, was suitable for preservation of isolated rat hepatocytes with respect to the maintenance of drug metabolism and levels of energy-rich substrates. METHODS: Viability of the isolated rat hepatocytes was determined by trypan blue exclusion, ATP content and energy charge after 24 and 48 h of storage in UW at 0 degrees C. Phase I and II metabolic functions of the cells were studied by measuring the cytochrome P450 content and the metabolic rate of lidocaine and 7-ethoxycoumarin. RESULTS: During 48 h of storage of hepatocytes in UW both phase I and phase II metabolism are preserved at control levels. After storage, the viability of the hepatocytes was not changed significantly, and the cells maintained proper cellular ATP content and overall energy charge. CONCLUSIONS: These results imply that hepatocytes from a single isolation can be stored in UW solution and used for metabolism experiments for 3 consecutive days, allowing a reduction in the use of experimental animals.

Animals↗

PubMed1997

Comparison of five incubation systems for rat liver slices using functional and viability parameters.

Precision-cut liver slices are presently used for various research objects, e.g. to study metabolism, transport, and toxicity of xenobiotics. Various incubation systems are presently employed, but a systematic comparison between these incubation systems with respect to preservation of slice function has not been performed yet. Therefore, we started a comparative study to evaluate five of these systems: the shaken flask (an Erlenmeyer in a shaking water bath), the stirred-well (24-well culture plate equipped with grids and magnetic stirrers), rocker platform (6-well culture plate with Netwell insert rocked on a platform), the roller system (dynamic organ culture rolled on an insert in a glass vial), and the 6-well shaker (6-well culture plate in a shaking water bath). The liver slices were incubated in these incubation systems for 0.5, 1.5, and 24.5 h and subsequently subjected to viability and metabolic function tests. The viability of the incubated liver slices was evaluated by: potassium content, MTT assay, energy charge, histomorphology, and LDH leakage. Their metabolic functions were studied by determination of the metabolism of lidocaine, testosterone, and antipyrine. Up to 1.5 h of incubation all five incubation systems gave similar results with respect to viability and metabolic function of the liver slices. However, after 24 h, the shaken flask, the rocker platform, and the 6-well shaker incubation systems appeared to be superior to the stirred well and the roller incubation systems.

Animals↗

PubMed1994

Characterization of transport in isolated human hepatocytes. A study with the bile acid taurocholic acid, the uncharged ouabain and the organic cations vecuronium and rocuronium.

The uptake and efflux of three categories of substrates were measured in isolated human hepatocytes and compared to those in rat hepatocytes. In addition, the extent to which the in vitro experiments quantitatively reflect liver function in vivo in both species was investigated. The anionic bile acid taurocholic acid was taken up by isolated human hepatocytes at a considerably lower rate than observed in isolated rat hepatocytes. Taurocholic acid uptake both in human hepatocytes and in liver plasma membrane vesicles showed sodium dependency. The uptake rate of taurocholic acid in isolated hepatocytes of both species was quantitatively compatible with the reported liver clearance of the bile acid in vivo. Ouabain uptake rate in isolated human hepatocytes was lower than in rat hepatocytes. This species difference was in accordance with pharmacokinetic studies in vivo on hepatic clearance of ouabain in man and rat. Uptake of vecuronium into human hepatocytes was about a factor of 10 lower than that in rat hepatocytes. Uptake into and efflux from human hepatocytes was comparable for the two short acting muscle relaxants vecuronium and rocuronium. Since distribution to the liver is considered to be a major factor in termination of action of vecuronium and rocuronium these observations were in line with the human pharmacokinetic profiles. In conclusion, the uptake rate of the studied model compounds in human hepatocytes appeared to be lower than that in rat hepatocytes. These observed transport rates reflected the relative hepatic transport rates observed in these species in the intact organism, but the absolute values in both species for some substrates may have been somewhat lower than calculated from in vivo data. It is concluded that transport studies in isolated hepatocytes are suitable for comparative drug transport studies, but are less precise in the prediction of quantitative membrane transport.

Androstanols↗

PubMed1993

Pharmacokinetic analysis and cellular distribution of the anti-HIV compound succinylated human serum albumin (Suc-HSA) in vivo and in the isolated perfused rat liver.

After intravenous injection of a low dose (25 micrograms/kg) in rats, the anti HIV-1 compound succinylated human serum albumin (Suc-HSA) is taken up mainly in the liver and spleen and is proteolytically degraded. Ten minutes after injection of 125I-Suc-HSA, 72 and 14% of the dose were found in the liver and spleen, respectively. With immunohistochemistry we demonstrated that in both organs, Suc-HSA was specifically endocytosed in endothelial cells. In the isolated perfused rat liver preparation, liver uptake was shown to be saturable, with a Km of 2.9 10(-8) M and a Vmax of 2.4 micrograms/min/100 g body weight. The apparent Km and Vmax in vivo were 2.2 10(-7) M and 10.3 micrograms/min/100 g, respectively. Uptake in liver and spleen was inhibited by preadministration of an excess of formaldehyde-treated albumin and with polyinosinic acid, indicating the involvement of the scavenger receptor, as anticipated for such polyanionic compounds. Suc-HSA is not absorbed intact from the colon and the ileum. After injecting (i.v.) rats with a high dose of Suc-HSA (10 mg/kg), the elimination t1/2 was 3 hr, and therefore, sustained plasma levels above the concentration needed for in vitro anti-HIV-1 activity can be achieved.

Animals↗

PubMedDate not supplied

Brain death causes structural and inflammatory changes in donor intestine.

UNLABELLED: Brain death donors are frequently used for transplantation. Previous studies showed that brain death (BD) negatively affects the immunological and inflammatory status of both liver and kidney. OBJECTIVE: Therefore we studied the inflammatory and morphological changes in donor small intestine after brain death induction. METHODS: BD was induced in rats by slow inflation of an epidural balloon catheter. Three groups (n = 6) were compared, 1 hour, 4 hours BD and sham operated controls. The liver was used as a reference to confirm our previous findings. Intestinal injury was determined using the Park score. Polymorphonuclear cells (PMNs) were counted in intestine and liver as a marker for inflammatory response. Real time PCR was used to demonstrate the effects of BD on ICAM-1 expression in the jejunum. RESULTS: The morphology of the intestine was compromised after 1 and 4 hours BD. In brain dead rats, apical lifting of epithelial cells was clearly present, which resulted in higher Park scores compared to controls (P < .05). Liver morphology remained intact. In small intestine and liver an increased PMN influx in the 1 hour BD group was observed in comparison to controls. Hepatic PMN influx increased further in the 4 hours BD group (P < .05). ICAM-1 was upregulated in jejunum in both the 1 hour BD and 4 hours BD groups compared to controls (P < .05). In conclusion, the early occurrence of intestinal damage after BD induction may negatively influence transplant outcome.

Animals↗

PubMedDate not supplied

The applicability of rat and human liver slices to the study of mechanisms of hepatic drug uptake.

In the present study we investigated the applicability of the liver slice model to study mechanisms of drug uptake. Four model compounds were investigated that enter hepatocytes via entirely different membrane transport mechanisms. Rhodamine B (RB), which enters hepatocytes by passive diffusion, was homogeneously distributed throughout the rat liver slice (250 microm thickness) within 5 min, indicating that the penetration rate into the slice and the diffusion rate into the cells are rapid. In contrast, lucigenin (LU), which is taken up by hepatocytes through adsorptive endocytosis, was detected in the inner cell layers after 15 min. Digoxin uptake into the slice showed a temperature-dependent component and was stereoselectively inhibited by quinine, which is compatible with the involvement of a carrier-mediated uptake mechanism. The neo-glycoalbumin Lactose(27)-Human Serum Albumin (Lact(27)-HSA) and the negatively charged Succinylated-Human Serum Albumin (Suc-HSA) entered the slices and were taken up temperature-dependently into hepatocytes and endothelial cells, respectively. The liver slice preparation is a valuable tool to investigate the mechanisms of cellular uptake of drugs. Moreover, the precision-cut liver slices offer the unique possibility to study both hepatocyte and endothelial cell function in human and rat liver.

Aconitic Acid↗