A quantitative study of carbohydrate metabolism in the normal and injured rat.

Abstract

This work arose out of study of the effect of severe injury on the metabolism of the rat. Its aim was to determine how carbohydrate metabolism differed in injured and normal rats. From the review of Levenson, Einheber & Malm (1961) it is clear that although the effect of injury on metabolism has been studied for a long time there is still much to be learnt. In the past, studies have been, for the most part, confined to determinations of the concentrations of metabolites in tissues. In the case of carbohydrate metabolism this is not enough. Besides concentrations of metabolites the rates of metabolism along the various pathways, glycolytic, gluconeogenic and oxidative, are also required. These rates can only be studied in whole animals by using tracers.We have, therefore, injected control and injured rats intravenously with U-14C-glucose, U-14C-fructose and 1_14C_, 2_14C-and 3-14C-pyruvates. We have followed the disappearance of 14C-glucose and 14C-fructose from the blood and the appearance and subsequent disappearance of 14C-glucose after the injection of 14C-fructose and the labelled pyruvates. The excretion of 14CO2 formed by the oxidation of these compounds in vivo was also followed. In this way the glycolytic and gluconeogenic pathways were spanned by 14C-glucose and 14C-pyruvate while 14C-fructose could be expected to provide information on processes in the middle, as its label enters them mainly as triose phosphate (Hers & Kusaka, 1953;Leuthardt, Testa & Wolf, 1953).Results obtained from experiments of this type show only the combined effects of distribution and metabolism. To separate these two effects one must find a method of interpretation which allows for their interaction. Unless this is done even qualitative conclusions may be wrong and it is quite impossible to make quantitative estimates. The only technique which offers some hope of separating distributive and metabolic processes is compartmental analysis (Sheppard, 1962). Theoretical models which reproduce the most important features of these processes are set up and analysed mathematically. No model can take account of all the processes, 13 Physiol. 179

Evidence for a Role of Glucocorticoids in the Development of Insulin Resistance After Ischaemic Limb Injury in the Rat

“…The rate of glucose production was calculated as the difference between the disposal rate measured with [5-3H]glucose and the net rate of loss of glucose from its distribution space, assumed to be 23-2 ml/100 g (Ashby, Heath & Stoner, 1965), while the glucose concentration was falling.…”

Effect of injury on shivering thermogenesis in the rat

“…Ta was kept at 200 C after removal of the tourniquets until the start of the test 1-1 5 hr later. By this time a steady state has been reached in the acute response to injury (Ashby, Heath & Stoner, 1965;Stoner, 1969). The arterial blood pressure at this stage is about 80 mm Hg (Stoner, 1961;Stoner & Little, 1969).…”

Evaluation of Carbohydrates in Parenteral Nutrition

“…About 70 % of the fructose is transformed into glucose (Ashby et al, 1965;Stoner and Heath, 1973). The part of fructose which is transformed into glucose requires for its further metabolism the presence of insulin .…”