Regulation of secretion of growth hormone, somatomedin-C and pancreatic hormones by amino acids in ruminants.

近年来，外源性GH对奶牛产奶量的影响引起了人们的广泛关注。生长激素的作用可能涉及刺激吸收的营养物质的分解，为乳腺提供产生能量的底物和可用于生产乳成分的底物。当体内的能量分配指向催化剂时。可以预期通过增加对乳腺的底物供应来提高产奶量。相比之下。合成代谢能量分配似乎是刺激牛肉生产所希望的。反刍动物和其他动物一样，能量分配的方向主要受代谢激素如GH、生长调节素-C（Sm-C）、胰岛素和胰高血糖素的调节，已知有几种氨基酸影响代谢激素的分泌。由于这些激素也是调节氨基酸代谢的中心，因此值得量化这些激素的水平。 关于我们 亮氨酸是刺激胰岛素分泌最有效的氨基酸，但对胰高血糖素和GH分泌没有任何增加作用。丙氨酸、甘氨酸和丝氨酸诱导的胰高血糖素和胰岛素分泌的增强作用大于其他氨基酸。没有氨基酸能够特异性刺激胰高血糖素分泌而不增加胰岛素或GH分泌。关于胰岛素和胰高血糖素的分泌，氨基酸可以根据其R结构进行分组。中性直链氨基酸刺激胰岛素和胰高血糖素分泌，对较短C链氨基酸的分泌反应更大。支链氨基酸倾向于增强胰岛素和抑制胰高血糖素分泌。酸性氨基酸引起GH分泌增加。天冬氨酸引起的GH分泌的最强刺激，超过精氨酸诱导。长时间的亮氨酸十二指肠内给药促进Sm-C分泌。少

Much attention has recently been Paid to the effects of the exogenous administration of GH in increasing milk production of dairy cows. The effect of GH could involve the stimulation of catabolism of absorbed nutrients providing energy-yielding substrates for the maffimary gland and substrates that can be utilized to produce milk constituents. When energy partition in the body is directed towards catabolism. one may expect an enhanced milk production via increased substrate supply to the mammary gland. By contrast. an anabolic energy partition appears to be desirable to stimulate beef production. In ruminant animals, as in the other species, the direction of energy partition toward catabolism or anabolism is mostly regulated by metabolic hormones such as GH, somatomedin-C (Sm-C), insulin and glucagon.Several amino acids are known to affect the secretion of metabolic hormones. As these hormones are also central to the regulation of amino acid metabolism, it is worthwhile to quantify the … More extent to which each amino acid can stimulate the secretion of these hormones.Leucine was the most effective amino acid in stimulating insulin secretion but did not produce any increase in glucagon and GH secretion. Alanine, glycine and serine induced a greater enhancement of both glucagon and insulin secretion than other amino acids. No amino acid was able to specifically stimulate glucagon secretion without also increasing insulin or GH secretion. As regards insulin and glucagon secretion, amino acids could be divided into groups according to their R-structures. Neutral straight chain amino acids stimulated both insulin and glucagon secretion, with a greater secretory response to shorter C-chain amino acids. Branched chain amino acids tended to enhance insulin and suppress glucagon secretion. Acidic amino acids caused an increase in GH secretion. Aspartic acid caused the strongest stimulation of GH secretion, exceeding that induced by arginine. Prolonged intraduodenal administration of leucine enhanced Sm-C secretion. Less