Liver hypoxia and lack of recovery after reperfusion at high blood alcohol levels in the intragastric feeding model of alcohol liver disease.

The purpose of this study was to test for the presence of liver hypoxia and recovery after reperfusion when blood alcohol levels (BAL) are high. Male rats were fed ethanol intragastrically at a constant rate for 1 month. The pO(2) levels were then measured on the liver surface of these rats, in vivo during laparatomy under isoflurane anesthesia. To measure the response to acute hypoxia, the hepatic blood flow was clamped off at the porta hepatis. When the clamp was released, recovery from hypoxia was measured. A number of hypoxic-inducible genes in the liver were analyzed by means of quantitative RT-PCR as a measure of increased activation of hypoxia initiated transcription. The mRNA levels of genes for adrenomedullin, adrenergic receptor alpha, 1a and 1d, CDK inhibitor 1a, and erythropoietin were all significantly higher at the peaks than troughs. Expression of these same genes in the livers of control rats fed dextrose was lower than at the troughs. Although the mRNA level of the hypoxia-inducible factor (HIF-1alpha) was higher at the trough than at the peak, its protein concentration in the nuclear fraction was not increased at the troughs compared with the peaks. In fact, the nuclear protein level of HIF-1alpha at the peak was significantly higher than in control samples, which is consistent with the presence of hypoxia at the peaks. Further analysis of the HIF-alpha degradation regulation revealed that prolyl 4-hydroxylase (P4ha1) and von Hippel-Lindau syndrome homolog (Vhl) were both up-regulated at the troughs compared with the peaks. The liver surface oxygen levels at the peaks were reduced compared with the control samples. The pO(2) levels fell abruptly when the vessels at the porta hepatis were clamped. When the clamp was removed, allowing reperfusion of the liver, pO(2) returned to baseline levels in the control, and at the troughs but not at the peaks. These results support the hypothesis that hypoxia occurs at the peaks of the BAL cycle and recovery from ischemia is impaired at the peaks.