Relationship between tissue mobilization and storage in the rat

Abstract

The amount of energy mobilized or stored as protein, expressed as a proportion of the total energy stored or mobilized (defined as the P ratio, Payne & Dugdale, 1977), was investigated in the young male (rapid growth) and adult female (slow growth) rat. Energy mobilization was induced by a 3 d fast and the changes in body content of fat and lean tissues were used to estimate the fasting P ratio (Pfast). Tissue storage was subsequently effected by 17 d of refeeding and the corresponding ratio (Prefed) was calculated from the amounts of lean and fat tissue regained. The same experimental protocol was used for measuring Pfast and Prefed in weanling (30d) and adult (130d) rats. Weightmatched individuals were assigned to three groups. All animals in group 1 were killed at the beginning of the experiment. Animals in group 2 were fasted for 3 d and then killed. Group 3 animals were first fasted for 3 d, then had free access to a stock diet for a further 17 d before being killed. During fasting, a close linear relationship was found between weight change and body energy changes (r 0.985, and r 0.92, P<O.OOl for weanlings and adult rats respectively) and between carcass N loss and urinary N loss (r 0.933, P < 0.001). These relationships were used to estimate the body energy and N content of each animal at the end of the initial fasting period. Hence, both Pf,, and Prefed values could be calculated for all individuals at both ages. When Pf,, and Prefed were calculated for adult rats, the mean values were similar (0.138 (SE 0.002) and 0.130 (SE 0.006) respectively). Individually, the Pf,, and Prefed values were correlated (r 0.54, P = 0.058). In weanling rats, the mean Prefed value was about 2.5 times the PfSt (0.421 (SE 0.0113) v. 0.156 (SE 0.004)). Despite the differences in Pfast and Prefed, the individual values were again correlated (r 0.668, P < 0.05). These results support the suggestion made by Payne & Dugdale (1977), that particular Pratio values are characteristic of individuals and describe the extent to which protein is mobilized or stored during fasting or refeeding. These observations are discussed in relation to the predictions made by the Payne-Dugdale model. Energy-protein mobilization: Energy-protein storage: P ratio

Relationship between birth weight and urea kinetics in children

“…It is possible that urea production resulting from amino acids oxidation is related to birth weight and drives urea salvage in later life. This is in keeping with the suggestion that the P-ratio is programmed in utero and is related to body composition (Payne and Dugdale, 1977;Henry et al, 1997).…”

“…The mechanism that accounts for the effects of the intrauterine environment on growth and body composition remains unclear. It is of interest that Payne and Dugdale (1977) and Henry et al (1997) have proposed that the fraction of total energy stored that is either deposited as protein or mobilized from protein, defined as the P-ratio, is programmed and is therefore characteristic of the individual. This infers that programming of the partitioning of amino acids between synthetic pathways and oxidative pathways in utero is part of the mechanisms that account for the effect of the intrauterine environment on growth in later life.…”

Effects of Short-term Fasting on Selected Physiological Functions in Adult Male and Female Japanese Quail

“…Food deprivation is associated with lowered nutrient absorption and decreased intestinal function that result from lowered activity of many absorbtive enzymes (Henry et al 1997). Alkaline phosphatase (AP) which is functionally involved in nutrient absorption and transport of long-chain fatty acids in intestinal mucosa, markedly decreases its activity after a short period (3-6 d) of food deprivation in rat (Holt and Kotler 1987;Kaur et al 1996;Raãek et al 2001).…”

Effects of a high-protein, low-energy diet in finishing lambs: 2. Weight change, organ mass, body composition, carcass traits, fatty acid composition of lean and adipose tissue, and taste panel evaluation

“…It is also the most problematic as it implies that r p must be a function of r f ; however it is not treated as such in the derivation of the model. Henry et al (1997) observed in a short-term cross-sectional study in rats high between-animal variation in estimates of the P ratio (the amount of energy mobilized or stored as protein, expressed as a proportion of total energy stored or mobilized). Similar work is lacking for ruminants, but would be very useful for understanding the nutritional constraints to ruminant production in extensive management systems.…”