EFFECT OF GLUCAGON ON PHENYLALANINE METABOLISM AND PHENYLALANINE-DEGRADING ENZYMES IN RAT
EFFECT OF GLUCAGON ON PHENYLALANINE METABOLISM AND PHENYLALANINE-DEGRADING ENZYMES IN RAT
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DOI：
10.1042/bj1420231
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发表时间：
1974-01-01
影响因子：
4.1
通讯作者：
HARPER, AE
中科院分区：
文献类型：
--
作者：
BRAND, LM;HARPER, AE
胰高血糖素皮下给药大鼠10天，对肝脏苯丙氨酸羟化酶活性没有显着影响，但诱导肝脏二氢蝶啶还原酶的两倍以上。在口服苯丙氨酸负荷的大鼠中，胰高血糖素治疗刺激氧化并抑制尿苯丙氨酸排泄。这些反应可能与胰高血糖素对肝脏酪氨酸-α-酮戊二酸氨基转移酶活性的影响无关。即使在大鼠苯丙氨酸羟化酶活性降低到50%的控制值旁路-氯苯丙氨酸管理，胰高血糖素治疗增加苯丙氨酸氧化率显着。虽然胰高血糖素处理的大鼠肝脏苯丙氨酸-丙酮酸转氨酶增加了10倍，但胰高血糖素处理并没有增加苯丙氨酸负荷大鼠苯丙氨酸转氨酶产物的尿排泄。胰高血糖素治疗不影响肠道或肝脏对苯丙氨酸的摄取，也不影响肝脏中苯丙氨酸羟化酶辅因子的含量。这表明，二氢蝶啶还原酶是在大鼠苯丙氨酸降解的限速酶，胰高血糖素可能通过间接促进维持苯丙氨酸羟化酶辅因子在其活性，还原状态调节苯丙氨酸氧化代谢率vivo。
Glucagon administered subcutaneously to rats for 10 days had no significant effect on liver phenylalanine hydroxylase activity, but induced liver dihydropteridine reductase more than twofold. In rats administered a phenylalanine load orally, glucagon treatment stimulated oxidation and depressed urinary phenylalanine excretion. These responses could not be related to an effect of glucagon on hepatic tyrosine–α-oxoglutarate aminotransferase activity. Even in rats with phenylalanine hydroxylase activity depressed to 50% of control values byp-chlorophenylalanine administration, glucagon treatment increased the phenylalanine-oxidation rate substantially. Although hepatic phenylalanine–pyruvate aminotransferase was increased tenfold in glucagon-treated rats, glucagon treatment did not increase urinary excretion of phenylalanine transamination products by rats given a phenylalanine load. Glucagon treatment did not affect phenylalanine uptake by the gut or liver, or the liver content of phenylalanine hydroxylase cofactor. It is suggested that dihydropteridine reductase is the rate-limiting enzyme in phenylalanine degradation in the rat, and that glucagon may regulate the rate of oxidative phenylalanine metabolismin vivoby promoting indirectly the maintenance of the phenylalanine hydroxylase cofactor in its active, reduced state.