Liver regeneration after partial hepatectomy in the rat. Sequential events monitored by 31P-nuclear magnetic resonance spectroscopy and biochemical studies.

BACKGROUND

Little data exist wherein both the 31P nuclear magnetic resonance (NMR) signals and biochemical changes associated with hepatic regeneration after a 70% hepatic resection have been assessed simultaneously.

EXPERIMENTAL DESIGN

Two groups of rats were used: one group underwent a 70% partial hepatectomy and the second underwent a sham operation. Both groups were followed sequentially for 192 hours by in vivo serial 31P-NMR spectroscopy of the liver and its phospholipid extracts. Liver injury and function were assessed by biochemical means.

RESULTS

After surgery, a significant reduction in ATP and an increase in the phosphomonoester signal for the hepatectomized animals were noted as compared with the controls (p < 0.05). The phosphodiester content of the liver in the hepatectomized rats declined to nonmeasurable amounts in vivo. The nadir of ATP occurred 72 hours after surgery. The area of the phosphomonoester relative to an external reference of methylenediphosphonic acid peak increased steadily over the first 96 hours, whereas that of the area ratio of the inorganic phosphate/methylenediphosphonic increased over the first 72 hours posthepatectomy. The intracellular pH declined sharply in the first 3 days, followed by a gradual recovery over the next 5 days. Little change in the intracellular pH was observed for the control animals. A significant increase in the area of the phosphorylethanolamine relative to an internal reference of methylenediphosphonic and a reduction in the glycerophosphorylethanolamine and glycerophosphorylcholine peaks were noted during the first four post-hepatectomy days as measured by 31P-NMR of perchloric acid liver extracts (p < 0.05).

CONCLUSIONS

It has been found that a concerted reduction in the intracellular ATP and intracellular pH coupled with an increase in inorganic phosphate and high levels of phosphorylethanolamine occur as a result of hepatic regeneration and the physiologic changes induced. These data demonstrated that a coordinated pattern of biochemical changes occur with and after hepatic regeneration. Moreover, NMR spectroscopy demonstrates an increase in phosphomonoesters and a decline in phosphodiesters during hepatic regeneration. These measures and, more specifically, the ratio of these two lipid classes may provide a biochemical snapshot of the regeneration status of the liver.