Abstract
Circadian rhythms were assessed in rats (224-246 grams) receiving either an intragastric (IG) or intravenous (IV) infusion continuously (C), or IG or IV infusions discontinuously (D) from 0000 to 1400 hours daily. A control group was maintained on a stock diet ad libitum. IV- and IG-fed rats were infused with 50 milliliters per day of a solution containing 25% dextrose and 4.25% amino acids plus vitamins and minerals. After 10 to 11 days, groups of rats were killed from each treatment every 6 hours over a 24-hour period. Results showed that IG feeding promoted better growth and nitrogen retention than IV feeding. Rhythm patterns for liver weight, glycogen, and protein content were similar between D-IG and D-IV infused rats. All groups except the D-IV fed rats exhibited fluctuations of serum insulin. A rhythm was not present for serum glucose in C-IV fed rats and a rhythm was also absent for serum albumin in both C-IV and D-IV fed rats. C-IV feeding increased serum glucose and insulin levels and decreased serum albumin levels in comparison to IG feeding. In comparison to the ad libitum-fed, control rats, C-IV or D-IV or IG infusions led to alterations in liver and serum parameters.
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