Glycolysis and energy metabolism in rat liver during warm and cold ischemia: evidence of an activation of the regulatory enzyme phosphofructokinase.

The current study was undertaken so that the effects of both ischemia and ischemia + hypothermia could be examined in mammalian liver. Particular reference was made to the function of glycolysis, which is the only mechanism for energy production under these conditions. The response of adenylate pools reflected the energy imbalance created during warm ischemia within minutes of organ isolation. ATP levels and energy charge values for control (freshly isolated) livers were 1.20 +/- 0.07 and 0.49 +/- 0.02 mumol/g. Within 5 min of warm ischemia, ATP levels had dropped well below control values and by 30 min warm ischemia, ATP, AMP, and E.C. values were 0.21, 2.01, and 0.17 mumol/g, respectively. Cold ischemic livers (flushed with Marshall's citrate solution and stored on ice) exhibited similar, but more protracted, patterns of adenylate depletion (ATP and ADP) and accumulation (AMP). In both warm and cold ischemic livers, levels of fructose-6-phosphate (F6P) and fructose-1,6-bisphosphate (F1,6P2) indicated a marked activation of glycolysis at the phosphofructokinase (PFK) locus after a certain time of ischemia. Although the activations occurred at different times (30 min and 10 h for warm and cold ischemic livers, respectively), the patterns of change in levels of glycolytic metabolites associated with the PFK-catalyzed reaction were similar; levels of F6P dropped and F1,6P2 increased. Changes in metabolite levels (phosphoenol pyruvate and pyruvate) associated with another key suspect regulatory enzyme, pyruvate kinase, indicated no role in regulatory control of glycolysis during warm or cold ischemia. The activation of PFK at 30 min and 10 h of warm and cold ischemia, respectively, may reflect the accumulating effects of loss of intracellular homeostasis, which leads to impending irreversible damage.

Liver metabolism in cold hypoxia: a comparison of energy metabolism and glycolysis in cold-sensitive and cold-resistant mammals.

The effects of cold hypoxia were examined during a time-course at 2 degrees C on levels of glycolytic metabolites: glycogen, glucose, glucose-1-phosphate, glucose-6-phosphate, fructose-6-phosphate, fructose-1,6-bisphosphate, phosphoenolpyruvate, pyruvate, lactate and energetics (ATP, ADP, AMP) of livers from rats and columbian ground squirrels. Responses of adenylate pools reflected the energy imbalance created during cold hypoxia in both rat and ground squirrel liver within minutes of organ isolation. In rat, ATP levels and energy charge values for freshly isolated livers were 2.54 mumol.g-1 and 0.70, respectively. Within 5 min of cold hypoxia, ATP levels had dropped well below control values and by 8 h storage, ATP, AMP, and energy charge values were 0.21 mumol.g-1, 2.01 mumol.g-1, and 0.17, respectively. In columbian ground squirrels the patterns of rapid ATP depletion and AMP accumulation were similar to those found in rat. In rat liver, enzymatic regulatory control of glycolysis appeared to be extremely sensitive to the decline in cellular energy levels. After 8 h cold hypoxia levels of fructose-6-phosphate decreased and fructose-1,6-bisphosphate increased, thus reflecting an activation of glycolysis at the regulatory step catalysed by phosphofructokinase fructose-1,6-bisphosphatase. Despite an initial increase in flux through glycolysis over the first 2 min (lactate levels increased 3.7 mumol.g-1), further flux through the pathway was not permitted even though glycolysis was activated at the phosphofructokinase/fructose-1,6-bisphosphatase locus at 8 h, since supplies of phosphorylated substrate glucose-1-phosphate or glucose-6-phosphate remained low throughout the duration of the 24-h period.(ABSTRACT TRUNCATED AT 250 WORDS)

A prospective randomized clinical trial of liver preservation using high-sodium versus high-potassium lactobionate/raffinose solution.

High-sodium as opposed to high-potassium lactobionate/raffinose preservation solution offers potential advantages in improving the quality of liver storage by reducing potassium-induced vasoconstriction and preventing hyperkalaemia on reperfusion. In our study we evaluated in a prospective trial (encompassing 40 consecutive cadaver donor hepatic retrievals and subsequent transplants) the efficacy of a high-sodium formulation versus the standard high-potassium solution. Quality of preservation was assessed by clinical indices of liver function in the intraoperative and early postoperative phases, including measurements of requirements for blood and blood products and potassium, circulating liver enzymes and bilirubin. Frequencies of acute rejection episodes and primary non-function were also recorded. No significant differences were evident in any of the measured parameters. Thus a sodium-based solution can be used for hepatic preservation, advancing the possibility that it may be possible to develop a single storage solution for clinical multi-organ donor operations.

Differences in blood supply to the cerebral cortex between sheep and calves during slaughter.

Using methylene blue boli, injected via an intracardiac catheter, the blood supply to the brain in two one- to 10-day-old calves and three adult sheep was studied during and after severance of the common carotid arteries and jugular veins. Passage of dye through cerebral vessels could not be observed in the exposed cerebrum of sheep after bilateral severance of major blood vessels. When vessels were severed on one side only, the passage of dye was noted for at least 53 seconds. In calves, after bilateral severance, sequential boli of dye could be detected passing through the cerebral vessels for more than 100 seconds. These results provide an explanation and support for the belief that there are major differences in the onset of insensibility between sheep and calves subsequent to severance of the common carotid arteries and jugular veins. The differences in blood supply to the brain which were demonstrated could be accounted for by differences in the blood supply to the brain by the vertebral artery in sheep and cattle. The effects of slaughter on the blood supply to the eye are discussed as a possible explanation of the disparity between results of studies in this general field which have used retinal responses in their investigations and those which have not.