| Research Abstract |
Insulin has a potency to stimulate deposition of major nutrients (carbohydrate, lipid and protein) in the animal body. Insulin secretion and action vary according to animal physiological conditions of ruminants. Therefore, metabolic regulation of insulin on utilization (oxidation) and storage of nutrients including glucose may vary under various physiological conditions of ruminants. The present experiment was designed to determine metabolic regulatin of insulin n the rate of oxidation and storage of nutrients in sheep under some physiological conditions.
1. Tissue responsiveness to insulin and the rates of oxidation of primary nutrients in hypomagnesemic sheep
(1) In hypomagnesemic sheep fed a low Malhigh K diet, insulin-induced glucose uptake was measured using a euglycemic clamp technlgue, and respiratiory gas analysis was performed to estimate oxidation rated of carbohydrate, fat and protein. Insulin-induced glucose uptake tended to decrease in the hyomagnesemic sheep. An rate of fat
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oxidation and decrease in carbohydrate oxidation were observed in hypomagnesemic sheep. These resulats ndicated that the hypomagnesemic animal stimulated fat oxidation rate, and suggested that decreased insulin actin may e involved in this phnomenon.
(2) The control and hypomagnesemic sheep were subjected to thermoneutral (20C) or cold (0C) environmenis for 7 days, and the euglycemic clamp technigue (EGC : 1, 2, 4, and 8mU/KgBw/min) and resipiratory gas analysis were performed to determine the rates of oxidation of primary nutrients and insulin action in both environments. Increases in heat production and the rate of fat oxidation were observed in the cold environment than in the thermoneutral environment. Insulin action as markedly decreased in hypomagnesemic sheep compared to those of control sheep in the cold enviroment. Insulin levels in the EGC techniqie did affect the rate of oxldation of prmary nutrients.
2. Effect of clenbuterol (beta-agonist) and insulin on the rate of oxidation of primary nutrients
(1) Sheep were administeraed clenbuerol (0,20 and 40 ug/kgBW/d) for 7 days. Then, sheep were subjected to respiratory analysis to deterine the rate of oxldation of primary nutrients. The clenbuterol treatment increased plasma FFA, fat oxidation rate and heat production. These results indicated that clenbuterol stimulated lypolysis and fat oxidation. Less
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