THE DIURNAL CYCLE IN THE LIVER

Abstract

The actual weight of the liver, and its water, glycogen, protein and fat content were determined at 9 A. M. after a 22-hr. fast, for 25 white rats. These data served as a control from which the changes in the livers of the experimental rats were estimated. All experimental rats were fed from 9 to 11 A. M. and 6 rats were killed at each 2-hr. interval thereafter for 46 hrs. The curve of hepatic weight changes was definitely bimodal. The peaks occurred at 7 and at 11 P. M., the low point occurring at 9 P. M. From 11 P. M. a continuous decrease was recorded so that at 7 the following morning the mean weight of the liver was essentially that of 24 hrs. before. The curve of the changes in water, glycogen, and to a less extent, protein, followed rather definitely the curve of the total hepatic weight change. The first mode occurred at 5 or 7 P. M. and the second at 11 P. M. or 1 A. M.; the low point occurred at 9 P. M. as in the total wt. curve.