The effect of PGE2 on hepatic blood flow and bile indocyanin green in the rat

Disorganization of microtubular network in postischemic liver dysfunction: its functional and morphological changes

Microtubules in the hepatocytes have been implicated to serve as lines of cytoplasmic transport of secretory materials, but are highly labile structures sensitive to pathological conditions in the cytosol. We examined the role of ischemia/reperfusion-induced cytoskeletal alterations in postischemic liver dysfunction. Rabbit livers were subjected to 60-min warm ischemia followed by 1 h or 24 h of reperfusion. Liver function was assessed by directly measuring hepatic clearance of indocyanine green (ICG), an organic anion whose cytoplasmic transport is assumed to depend on intact microtubules, using near-infrared spectroscopy. Structural alterations of microtubules were observed immunohistochemically using tissue sections stained with monoclonal anti-beta-tubulin antibody. ICG removal from hepatocytes into bile canaliculi deteriorated 1 h but reversed 24 h after reperfusion. Immunohistochemistry showed fragmentation of microtubules at the end of liver ischemia. This cytoskeletal alteration was evident 1 h but was not observed 24 h after reperfusion. Treatment with prostaglandin E1 exerted its beneficial effect by preserving ICG clearance and microtubular network. These results demonstrate that liver ischemia and subsequent reperfusion both affect the organization of microtubular network and suggest that structural disruption of microtubules may be a cause of postischemic liver dysfunction.

Plasma prostaglandin E1 concentrations and hemodynamics during intravenous infusions of prostaglandin E1 in humans and swine

Prostaglandin (PG) E1 administered intravenously has been used for the treatment of primary nonfunction of hepatic allografts and fulminant hepatic failure. It has been proposed that this therapy may improve hepatic blood flow via the vasodilating properties of PGE1. However, PGE1 undergoes extensive metabolic inactivation by the lung and the concentration of PGE1 reaching the liver during intravenous administration has not been determined. Thus, we measured plasma PGE1 concentrations in patients with hepatic dysfunction being treated with PGE1 and in a swine model of PGE1 infusion. We also determined the hemodynamic effects of PGE1 infusion in swine. Blood was sampled from the pulmonary artery, carotid artery, portal vein, and hepatic vein in swine infused with PGE1 (range, 0.67-4.9 microg/kg/hr) demonstrating: (1) a pulmonary extraction ratio of PGE1 of 0.78 +/- 0.12, (2) a splanchnic extraction ratio of PGE1 of 0.54 +/- 0.23, and (3) levels of PGE1 in the systemic circulation of </= 78 pg/ml, even at the highest infusion rates. Despite significant increases in body temperature and pulse rate, hepatic hemodynamics were not affected by the PGE1 infusions in healthy swine. Seven patients receiving intravenous PGE1 for hepatic dysfunction (0.11-1.30 microg/kg/hr) had a pulmonary extraction ratio of 0.69 +/- 0.17. Systemic arterial concentrations of PGE1 were </= 62 pg/ml. These results suggest that due to clearance of PGE2 in the pulmonary and splanchnic circulations, current clinical protocols for intravenous administration of PGE1 are not likely to affect perihepatic hemodynamics.

Alpha interferon has no effect on lidocaine metabolism in the rat

Interferons (IFN) inhibit activity of many isoenzymes of the hepatic microsomal cytochrome P-450 system. This inhibition is species specific. Lidocaine is metabolized by cytochrome P-450 III A 4. We investigated in the rat the effect of rat alpha-IFN on lidocaine elimination and on its extraction by the isolated perfused rat liver. To determine elimination, the femoral artery and vein were cannulated. 24 h later, the conscious rat was given lidocaine through the venous catheter and blood was drawn from the arterial catheter for lidocaine determination every 3 min for 20 min. 7 rats were pre-treated with intramuscular rat alpha-IFN 7.5 x 10(5) U, 24 h prior to the experiment and another 4 rats were given saline i.m. The lidocaine elimination rate constant was unchanged, 0.065 min-1 and 0.063 min-1 for the control and IFN groups, respectively. To investigate lidocaine extraction, the isolated perfused rat liver was used. Perfusate samples from the portal and hepatic veins were drawn at 2 min intervals for 20 min, and lidocaine extraction determined. Extraction was determined in two groups of 6 rats each. The first group served as control and these rats were injected with saline only, while in the second group, the rats were pre-treated with rat alpha-IFN 7.5 x 10(5) U. Lidocaine extraction by the isolated perfused rat liver remained unchanged, 97.0 +/- 0.7% and 94.0 +/- 2.4% in the control and IFN treated groups, respectively. It is concluded that the rat alpha-IFN affects neither the elimination nor the extraction of lidocaine.

Cimetidine and omeprazole do not affect cyclosporine disposition by the rat liver

Cyclosporine has been used with increased frequency, occasionally in conjunction with cimetidine and omeprazole. The present study was undertaken to study a possible interaction between either of the two drugs and cyclosporine in the liver. The isolated perfused rat liver was used with recirculation of perfusate for 150 min. 6 experiments were performed with each of the following: cyclosporine alone, cyclosporine with cimetidine, and cyclosporine with omeprazole. Initial concentrations of cyclosporine, cimetidine and omeprazole were 600 micrograms/ml, 12.5 micrograms/ml, and 4.5 micrograms/ml, respectively. At 1 and 2 h of perfusion 1 micrograms of omeprazole was added to perfusate. Cyclosporine concentration was determined at 30 min intervals. Results at 150 min expressed as percentage of the initial concentration of cyclosporine were 59 +/- 3%, 55 +/- 6%, and 60 +/- 9% for cyclosporine alone, with cimetidine and with omeprazole, respectively. The elimination rate of cyclosporine by the liver did not change during the entire experiment with the addition of cimetidine or omeprazole. Thus, it is concluded that short administration of cimetidine or omeprazole will not affect cyclosporine metabolism by the liver.

Recovery of hepatic clearance and extraction following a release of common bile duct obstruction in the rat

The rate of recovery for hepatic clearance and extraction following release of common-duct obstruction was investigated in the rat. Male Wistar rats underwent ligation of a cannulated common bile duct. Two weeks later, the cannula was opened and implanted into the duodenum, thus re-establishing enterohepatic circulation. Hepatic extraction and indocyanine green clearance were determined in three groups of six rats each, which differed by the time elapsed from the re-establishment of communication between the common bile duct and duodenum, i.e., 1, 48 and 168 h, respectively. A fourth group, in which a sham operation was performed, served as a control. Clearance was reduced from 16.9 +/- 2.5 ml/min per kg in the control group to 2.9 +/- 0.8, 5.4 +/- 2.4, and 8.5 +/- 3.3 ml/min per kg 1, 48, and 168 h, respectively, after release of common-bile-duct obstruction. Extraction rate was reduced from 37.3 +/- 5.9% to 17.5 +/- 2.7% in the 1st hour and recovered completely at 1 week. Thus, in the rat, release of a 2-week common-bile-duct obstruction is associated with complete recovery of the extraction capacity of the liver within a week, but only incomplete recovery of clearance. This decrease in clearance seems to be due to a decrease in effective hepatic blood flow, mostly probably due to the development of porto-systemic shunts.

Successful reversal of primary graft non-function in a liver transplant patient treated with prostaglandin E1

A 63 year old woman with liver failure received a transplant from a 21 year old male diagnosed as brain dead following a motor accident. After the operation, bile production was virtually absent and aspartate transaminase (AST) values rose dramatically 40 h postoperatively. Primary non-function of the graft was diagnosed, and the patient put on an urgent list for retransplantation. At the same time a continuous intravenous infusion of PGE1 was administered. Aspartate transaminase levels decreased within 9 h and reached normal levels by the sixth postoperative day, when bile production began to increase. Liver function subsequently returned to normal.

Cimetidine and omeprazole have different effects on hepatic extraction of lidocaine in rats

The effect of two antisecretory drugs, omeprazole and cimetidine, on the hepatic extraction of indocyanine green and lidocaine was studied in the isolated perfused rat liver. Both indocyanine green and lidocaine are removed by the liver with high extraction efficiency in a flow-dependent manner. The elimination of lidocaine, but not indocyanine green, involves metabolism by the mixed-function oxidase in the liver. A selective effect on the hepatic extraction of lidocaine, but not indocyanine green, may therefore indicate an inhibition of hepatic mixed-function oxidase. To test this hypothesis, a nonrecycling system at a fixed perfusion flow rate was used to measure the extraction of lidocaine. Under control conditions, the extraction rate of lidocaine was 83% +/- 8%. In the presence of omeprazole at concentrations of 0.9, 2.0, and 4.5 micrograms/mL, the extraction rates were 81% +/- 9%, 82% +/- 7%, and 75% +/- 7%, respectively. These changes were not significantly different than control rates. In contrast, the increasing concentrations of cimetidine caused significant decreases in the hepatic extraction of lidocaine to values of 78% +/- 8%, 63% +/- 14%, and 48% +/- 14% at concentrations of 0.25, 0.50 and 1.25 micrograms/mL, respectively. The hepatic extraction of indocyanine green, 39% +/- 6%, was not affected by the administration of either omeprazole or cimetidine. Thus, in the rat, omeprazole seems to be a less potent inhibitor of cytochrome P-450 than cimetidine.