In general, beta-adrenergic agonists partition the nutrient supply to increase muscle growth and decrease fat deposition. Use of exogenous agents such as beta-agonists allows measurement of changes occurring during manipulated growth as a model for physiological controls that may alter nutrient partitioning during normal growth. A better understanding of controls important in increasing lean tissue growth will increase our ability to alter the controls to stimulate lean growth. The mechanisms of importance in regulation of nutrient partitioning during normal or manipulated growth may include a change in tissue sensitivity or responsiveness to a hormone or metabolite. Insulin is a key metabolic hormone in ruminant and nonruminant animals.
Several studies suggest involvement of insulin in the mechanism of action of -adrenergic agonists.
The euglycemic clamp technique is a useful approach to the study of insulin sensitivity and responsiveness in an animal. The principle of the clamp is to control blood concentration of glucose under conditions of hyperinsulinemia resulting from infusion of insulin. Without the infusion of glucose, blood glucose concentrations would decline. Thus, by using the clamp technique one is able to study the effect of insulin on metabolic processes without the confounding effects of hypoglycemia. Experimental Procedures Six Herford x Angus steers were used in the experiment.