Hepatectomized Rabbits Research Articles

Kinetic analysis of ATP-synthetase and ATPase in regenerating rabbit liver.

The activities of ATP-synthetase and ATPase in rabbit liver were evaluated by kinetic analysis of rapid changes in ATP during alteration of oxygen supply, and were compared between normal and hepatectomized rabbits. Velocity constants of ATP-synthetase and ATPase were computed on the assumption that ATP-synthetase and ATPase follow the pseudo-first order reaction of ADP and ATP, respectively. The velocity constant of ATPase increased from the control value of 0.21 to 0.48 (min-1) in the remnant rabbit liver at 24 h after 70% hepatectomy. The velocity constant of ATP-synthetase increased from the control value of 4.05 to 5.24 (min-1) after the hepatectomy. These results indicate that both ATP-synthetase and ATPase are accelerated due to liver regeneration.

Glucose intolerance and amino acid imbalance in relation to changes in blood ketone body ratio in hepatectomized rabbits.

Glucose metabolism and plasma amino acid pattern were investigated in relation to arterial blood ketone body ratio (acetoacetate/3-hydroxybutyrate), which reflects liver mitochondrial redox state, in rabbits subjected to graded hepatectomy (25, 70 and 93%) and 70% hepatectomy with common bile duct obstruction. After partial hepatectomy, blood ketone body ratio decreased according to the extent of resected mass. Common bile duct ligation induced a further decrease in blood ketone body ratio in 70% hepatectomized rabbits. During a 6-hour hypertonic glucose infusion (0.7 g glucose/kg/h) which started 24 h after the operation, the blood glucose level remained between 230 and 280 mg/dl in 25 and 70% hepatectomized groups, while it increased linearly in 93% and jaundiced 70% hepatectomized groups. The plasma concentrations of alanine and proline as well as other amino acids increased as the blood ketone body ratio decreased. It is suggested that Krebs cycle and gluconeogenesis activities are inhibited as blood ketone body ratio decreases markedly resulting in an impaired glucose tolerance and amino acid imbalance.

Turnover of tissue plasminogen activator in normal and hepatectomized rabbits

The distribution, and clearance of the tissue plasminogen activator (tPA) was studied in rabbits, rats and mice. Following an intravenous injection of I-labelled tPA a large portion of the radioactive dose was rapidly accumulated in the liver. After one hour the radioactivity in the liver was less than 5 per cent of the injected dose. The highest activity was then found in the intestine, stomach and in the blood. Gel filtration of plasma taken one hour after the injection revealed that the major part (60%) of the radioactivity was present as low molecular- weight metabolites or free iodine The remaining activity was present as high molecular weight inhibitor complexes (26%) or as free tPA (15%). In order to study in vivo reactions between tPA and plasma inhibitors without hepatic interference, plasma turnover was also studied in hepatectomized rabbits. High amounts of radioactivity remained in the plasma after one hour. Gel filtration of this plasma revealed that 54 per cent of the radioactivity was bound to inhibitors, 34 per cent circulated as free tPA while a minor portion (12%) was found as free iodine or metabolites. The half-life of fibrinolytically active tPA in hepatectomized rabbits was 40 minutes compared to 2 minutes in intact rabbits. The increase in the half-life of tPA in hepatectomized rabbits also resulted in an improved thrombolytic effect after treatment with 0.5 mg tPA.

Changes in blood glucose levels in relation to blood ketone body ratio following hypertonic glucose infusion in 70% hepatectomized rabbits.

The effects of postoperative infusion of a hypertonic glucose solution on the blood glucose level, blood ketone body ratio (acetoacetate/beta-hydroxybutyrate), and plasma alanine and proline levels were studied in 70% hepatectomized rabbits (group A) and in rabbits 70% hepatectomized and, in addition, subjected to bile duct obstruction at 12 h after hepatectomy (group B). Glucose infusion was started at the end of hepatectomy and continued for 20 h. The blood glucose level in group A remained at approximately 300 mg/dl throughout the study; however, it reached 789 mg/dl in group B at 20 h. The blood ketone body ratio, which reflects hepatic mitochondrial redox potential, decreased from 0.90 +/- 0.09 in untreated rabbits to 0.38 +/- 0.05 in group A, and to 0.19 +/- 0.03 in group B at 20 h. As the blood ketone body ratio decreased, plasma proline and alanine levels increased rapidly (proline, r = -0.601, p less than 0.02; alanine, r = -0.640, p less than 0.001). In addition, the blood ketone body ratio was positively correlated with the hepatic energy charge level [(ATP + 0.5 ADP)/(ATP + ADP + AMP)] (r = 0.57, p less than 0.001). It is suggested that the entry of glucose and amino acids into the Krebs cycle is inhibited as the blood ketone body ratio decreases, and under such conditions the infused glucose tends to accumulate, resulting in severe hyperglycemia.

Relationship between initial hepatic uptake of indocyanine green and hepatic energy status in hepatectomized rabbits.

The relationship between initial hepatic uptake of indocyanine green (ICG) and hepatic energy status was studied in about 70% hepatectomized rabbits. At 24 h after hepatectomy, the initial plasma disappearance rate (K) and the maximal removal rate (Rmax) of ICG fell to 27 and 26%, respectively, and the mitochondrial phosphorylative activity was enhanced maximally with a concomitant decrease in the energy charge ( (ATP+1/2ADP)/(ATP+ADP+AMP) ) level. Afterward, the initial reduction of ICG removal rate was followed by a rapid increase in week 1 and more gradual return to preoperative values by week 6 after hepatectomy. In the early period after hepatectomy (1-7 days), the mitochondrial phosphorylative activity was the higher the smaller the %K value was, while in the late period after hepatectomy (1-6 weeks), the mitochondrial phosphorylative activity remained unchanged irrespective of increasing %K. It is suggested that the mitochondrial phosphorylative activity may be a better guide to evaluate the functional status of the remnant liver than the initial hepatic uptake of ICG, especially in the early period after hepatoctomy.

Changes in hepatic energy charge, blood ketone body ratio, and indocyanine green clearance in relation to DNA synthesis after hepatectomy

The changes in the energy charge (ATP+0.5ADP)/ (ATP+ADP+AMP) levels of the remnant liver were studied in relation to changes in the incorporation rate of methyl- 3H-thymidine into DNA, the blood ratio of acetoacetate/β-hydroxybutyrate and indocyanine green (ICG) clearance in 70% hepatectomized rabbits. The energy charge levels of the remnant liver decreased rapidly to 0.767 from 0.856 of normal, despite a marked enhancement of mitochondrial phosphorylative activity, concomitant with the fall in blood ketone body ratio, before a maximal increase of DNA synthesis after hepatectomy. Blood ketone body ratio was correlated with hepatic energy charge (r=0.696, p<0.01). After a maximal increase of DNA synthesis, hepatic energy charge levels and the blood keton body ratios increased gradually to normal levels, concomitant with a rise in ICG clearance. Energy charge levels of the remnant liver can be evaluated by the blood ketone body ratio.

Effects of hypothermia on energy metabolism of metabolically loaded liver.

The effects of hypothermia on adenine nucleotide level, mitochondrial metabolism and redox state of the remnant liver were studied in 25, 50, 70 and 93% hepatectomized rabbits. In 25% of the hepatectomized rabbits, energy charge levels and mitochondrial phosphorylative activities remained unchanged, while in 50 and 70% hepatectomized rabbits, the energy charge levels decreased maximally at 24 hours after hepatectomy with a concomitant rise of mitochondrial phosphorylative activity. In 93% hepatectomized rabbits, the energy charge levels decreased rapidly without enhancement in mitochondrial phosphorylative activity and these rabbits died within 12 hours after hepatectomy. Body cooling significantly increased the energy charge of the remnant liver with further enhancement in mitochondrial phosphorylative activity in 25, 50 and 70% hepatectomized rabbits, but did not increase the energy charge in 93% hepatectomized rabbits. On the other hand, during body rewarming, the energy charge levels of the remnant liver decreased. More than 60% of 70% hepatectomized rabbits died during body rewarming, while all of 50% or less hepatectomized rabbits remained alive. Thus, body cooling may provide remarkable protection for the remnant liver from an energy crisis under the condition that compensatory mitochondrial enhancements are present.

Circulating hepatodepressant factors decreasing the energy charge levels of the remnant liver after hepatectomy.

In 25% hepatectomized rabbits, the mitochondrial phosphorylative activity and the energy charge [(ATP + 1/2 ADP)/(ATP + ADP + AMP)] levels of the remnant liver remained unchanged after hepatectomy. In 70% hepatectomized rabbits, the energy charge levels of the remnant liver decreased maximally 24 h after hepatectomy (p less than 0.001), simultaneously with a marked enhancement of mitochondrial phosphorylative activity (P less than 0.001). Afterward, both returned to normal levels within 4 days. In 93% hepatectomized rabbits, the energy charge levels fell rapidly, with an inhibition of mitochondrial phosphorylative activity, within 6 h after hepatectomy. When a 24-hour 70% hepatectomized rabbit was cross-circulated with a normal rabbit, the energy charge in the liver of the normal partner decreased to 0.732 at 30 min after the blood exchange and then returned to 0.855 while that in the remnant liver of the hepatectomized partner increased from 0.767 to 0.820 (p less than 0.001). Also, the energy charge values of a 24-hour 70% hepatectomized rabbit were increased by the extracorporeal normal liver perfusion. It is suggested that a decrease in the energy charge of the remnant liver is due, at least partly, to the accumulation of the substances consuming hepatic energy (hepatodepressant factors) in the systemic blood of hepatectomized rabbits.

Changes in predominant energy substrate after hepatectomy

The changes in the energy substrate utilized by the remnant liver were studied in relation to the changes in the cellular energy status of 25 and 70% hepatectomized rabbits. In 25% hepatectomized rabbits, the energy charge ( ( ATP+0.5 ADP) ( ATP+ ADP+ AMP) ) level of the remnant liver remained unchanged, the energy substrate of which was predominantly glucose, rather than fatty acid. In contrast, in 70% hepatectomized rabbits, the energy production by the mitochondria was mainly dependent upon fatty acid oxidation at the early period after hepatectomy when the energy charge level decreased remarkably, and then upon glucose oxidation, concomitant with the restoration of the energy charge. It is suggested that the changes in the energy substrate utilized are closely related to those in the energy charge level and the mitochondrial phosphorylative activity of the remnant liver following hepatectomy.

A blood-borne factor stimulating hepatic biosynthetic process in hepatectomized rabbits

By measurement of energy charge (ATP+1/2ADP / ATP+ADP+AMP) and mitochondrial phosphorylative activity in liver tissue, it was possible to estimate the states of ATP generation and ATP utilization of normal and regenerative liver. In the liver of partially hepatectomized rabbits, a characteristic decrease in energy charge and increase in mitochondrial phosphorylative activity as compared with those of normal liver were noted, consistent with the notion that ATP-consuming reactions such as protein and nucleic acid syntheses are enhanced in the regenerative process. When normal or hepatectomized rabbits were singly circulated extracorporeally, the mitochondrial phosphorylative activity increased with a concomitant rise in energy charge. In cross-circulation between normal and hepatectomized rabbits, the energy charge of the normal partner decreased markedly with a concomitant elevation in mitochondrial phosphorylative activity, while those in the remnant liver of the hepatectomized partners were not significantly different from those of singly circulated hepatectomized rabbits. The decreased energy charge levels of the normal partner were prevented by the premedication of insulin without a significant effect to the hepatectomized partner. It is suggested that there is a humoral factor stimulating the hepatic energy-requiring biosynthetic process in the blood of hepatectomized rabbits.

Effects of cortisone on lipid and cholesterol metabolism in the rabbit and rat

Cortisone, 5 mg/day, first increased the plasma triglyceride levels of 2.5-kg male rabbits fed stock, high-fat, fat-free, or semistarvation diets. Later, hypercholesteremia was observed only in those plasmas in which triglyceride levels exceeded 400 mg/ml. Cortisone diminished accumulation of stainable fat in livers of animals fed fat, and of carbon particles in Kupffer cells; it caused parenchymal cells to enlarge and show vacuolization, abnormal nuclei, and fragmented cell walls. Rate of loss from plasma of parenterally administered triglyceride was similar in cortisone-treated and hepatectomized rabbits. Cortisone did not alter: lipid absorption, liver cholesterol, incorporation of acetate into cholesterol, bile cholesterol, rate of exit of cholesterol from plasma, Triton-induced hyperlipemia, or lipoprotein-lipase. Concentration of liver glycogen did not correlate with cortisone-induced lipemia. The authors suggest that cortisone induces hypercholesteremia only indirectly as a result of a sufficient degree of preceding hypertriglyceridemia, which stems in part from a relative inability of the liver to remove triglyceride from plasma.

CONVULSIVE SYNDROME IN RABBITS INJECTED WITH FAT EMULSION AND HEPARIN.

Functionally hepatectomized rabbits showed convulsions and coma within 2 hours after the intravenous injection of fat emulsion and heparin. Intravenous injection of the detergent triton prevented this syndrome, if given before the fat emulsion and heparin, and reversed it if given subsequently. Extremely high plasma non-esterified fatty acid levels were noted in rabbits showing the convulsive syndrome, but not in animals that received the detergent. The mechanism of the convulsions probably includes the toxicity of high amounts of non-esterified fatty acids.

THE LIVER AS THE SOURCE OF FIBRINOGEN

In hepatectomized rabbits a progressive decrease in blood fibrinogen occurs. Partial defibrination in the liverless rabbit invariably results in a progressive decrease in blood fibrinogen preceded by a temporary and slight rise. No evidence has been secured of fibrinogen regeneration in the absence of the liver. From this it follows that the liver is the essential source of fibrinogen and in all probability the sole one.

The Source of Fibrinogen.

The formation of fibrinogen has been ascribed to many tissues and organs of the body. Whipple, Goodpasture and others suggested that this substance takes its origin from the liver and intestinal tract; and recently Foster and Whipple have presented excellent evidence that the liver is the main if not the sole source of fibrinogen. Schultz, Nicholes and Schaefer have produced corroboratory data. Final proof in the matter has waited, however, upon the findings in liverless animals. In 4 hepatectomized rabbits we have determined the concentration of blood fibrinogen before operation and at various periods thereafter. A postoperative decrease in the substance was always found. In 6 others a partial depletion of fibrinogen was accomplished after hepatectomy and its concentration in the blood was followed until death. Controls subjected only to defibrination were also studied. The initial defibrination was accomplished under ether anesthesia by slowly injecting into the jugular vein 100-150 cc. of compatible defibrinated blood while removing an identical quantity from the carotid artery. The procedure was repeated 4 or 5 times. This reduced the blood fibrin concentration to one third to one fifth its original amount. By continuing the blood exchange a still greater reduction was sometimes brought about in the controls. Fibrinogen was estimated in the form of fibrin by the method of Foster and Whipple as modified by Schultz, Nicholes and Schaefer. In the controls fibrinogen regeneration was exceedingly rapid. Within 5 or 6 hours after a 90% reduction, a complete return to the previous amount was observed, regeneration far more rapid than has been reported for the dog. Twenty-four hours later the concentration had reached a level 50% above the normal figure and in two instances it had doubled within 48 hours. The findings were wholly different in the liverless rabbit. In 6 animals blood fibrin determinations were made immediately after the hepatectomy and then the partial defibrination was carried out, reducing the circulating amount by 65 to 80%.