Proton nuclear magnetic resonance of regenerating rat liver after partial hepatectomy.

Spin-lattice (T1) and spin-spin (T2) proton nuclear magnetic resonance relaxation times were measured over a 48-hours period of experimental liver regeneration in Wistar rats. T2 showed an early significant increase reaching a plateau 30% above baseline from the 10th hrs onwards. Laparotomized control animals showed no change in T2 values. The increase in T1 occurred at a later stage but was no different from that in laparotomized controls. T1 reached a peak, 20% above baseline, around the 30th hr. The changes observed were far less marked than those previously described for cancer tissue, which showed about a 60% increase in T1. Liver T1 fluctuations followed a circadian pattern, with a minimum at night's end and a maximum around mid-day. No circadian rhythm was seen for T2. The observed T1 and T2 changes were discussed with respect o mitotic and metabolic events known to occur during regeneration of the liver.