Plasma Composition of Insulin

I NSULIN is essential for the normal metabolism of carbohydrates, lipids and proteins in the monogastric animal (Tepperman, 1968) ; however, its role in the normal metabolism of ruminants is poorly understood. Since alloxan-induced diabetes produced a similar response in ruminant and nonruminant animals (Reid, Hinks and Mills, 1963; Jarret, 1946) and depancreatized sheep behaved similarly to alloxan-treated animals (Jarret and Potter, 1953), insulin is apparently important in carbohydrate metabolism by ruminants. Additional evidence supporting an important role of insulin in ruminant animals was obtained when insulin release from the pancreas was shown to occur following an elevation of the blood levels of glucose and fructose (Manns and Boda, 1967) and of propionic and butyric acids (Manns, Boda and Willes, 1967). In other studies, plasma levels of the non-esterified fatty acids of ruminants were depressed by insulin administration (Kuhlemeier and Trenkle, 1966). Ruminants responded to insulin-induced hypoglycemia with symptoms ranging from mild lassitude to severe convulsions (Reid, 1951a, b). Loss of nitrogen by the diabetic sheep has been observed (Reid, 1950a, b), but the role of insulin was not investigated. The present study was undertaken to investigate the influence of insulin on the circulatory amino acids of sheep with concomitant observations on circulatory glucose and acetate.