Circadian Fluctuations in Liver and Blood Parameters in Rats Adapted to a Nutrient Solution by Oral, Intravenous and Discontinuous Intravenous Feeding

Abstract

Liver and blood parameters were assessed in 200 g rats fed a fat-free hyperalimentation diet (25% dextrose + 4.25% amino acids) by different techniques. Fifty milliliters of the diet solution were fed by continuous intravenous (i.v. ) infusion, by discontinuous i.v. infusion from 0000 to 1400 hours, or orally by giving the diet at 0000 hours and allowing the rats to drink the entire volume. Results demonstrated that orally and discontinuously i.v. fed rats had similar circadian fluctuations in hepatic weight, glycogen and protein content. In comparison with orally fed rats, average daily levels of these liver parameters showed greater alterations in rats infused on a continuous rather than on a discontinuous basis. Serum urea levels showed circadian fluctuations in orally fed rats while the pat terns were arrhythmic in the two groups fed i.v. Serum total protein con centrations decreased in all groups, which was due primarily to diminished albumin levels. Glucose and insulin concentrations were lower with dis continuous i.v. feeding than with continuous i.v. feeding. It is suggested that under i.v. feeding, discontinuous infusion is tolerated better than is continuous infusion. The hypertonic alimentation diet used in these studies does not support normal albumin levels when fed either orally or intra venously. This may be associated with changes in serum fatty acid levels in relation to the transport function of albumin. J. Nutr. 110: 558-566,