Effect of deuterium on the circadian period and metabolism in wild-type and tau mutant Syrian hamsters

Homozygous tau mutant Syrian hamsters (tau-/-) have a free-running circadia n period (tau) around 20 h and a proportionally higher metabolic rate compa red with wild-type hamsters (tau+/+) with a period of circa 24 h. In this s tudy, we applied deuterium oxide (D2O) to hamsters to test whether deuterat ion affects the circadian period of locomotor activity and metabolic rate i n both genotypes. Running wheel activity and the metabolic rate were measur ed in constant illumination before, during, and after administration of 25% deuterium in drinking water. Wild-type hamsters lengthened their circadian period by 1.19 h (SD = 0.29 h) due to D2O application and tau-/- hamsters by 1.20 h (SD = 0.39 h). Deuteration changed neither the amount of activity nor the duration of activity phase (alpha) in either genotype. The mass sp ecific average metabolic rate (AMR, the oxygen consumption over 24 h) and t he mass specific resting metabolic rate (RMR) did not differ during deutera tion compared with non-deuteration conditions for either genotype. Both wit h and without D2O, tau-/- hamsters had higher metabolic rates than tau+/+ h amsters. There was no correlation between changes in the circadian period o f locomotor activity and metabolic rates caused by D2O. (C) 2000 Elsevier S cience Inc. All rights reserved.