Güttler F, Kühl C, Pedersen L, Påby P
Scand J Clin Lab Invest. 1978 May;38(3):255-60. doi: 10.3109/00365517809108420.
An oral phenylalanine load provokes a significant drop in serum tyrosine levels in children with phenylketonuria [8]. The aim of the present investigation was to examine the response of insulin and glucagon to oral phenylalanine loading as these hormones are known to have a hypoaminoacidaemic effect. Six adult normal weight and healthy men were loaded orally with 0.6 mmol L-phenylalanine per kg body weight after an overnight fast. Serum phenylalanine increased within 10 min after the load and reached a maximum concentration at 30 min. Serum tyrosine increased within 10 min after the load and reached a maximum concentration at 2 h. Plasma glucagon and insulin increased during the first 10 min after the load and reached a peak twice the fasting levels at 30 min after the load. The molar insulin/glucagon ratio remained unchanged during the first 20 min after the load but then declined by 50% at 2 h. Associated with this decline plasma amino acid concentration (except phenylalanine and tyrosine) declined by approximately 15%. The decline was most marked for isoleucine, leucine, methionine and valine. As the hypoaminoacidaemic effect of insulin and glucagon is known to be most marked for these four amino acids plus phenylalanine and tyrosine, the response of insulin and glucagon to a phenylalanine load may influence not only the fate of phenylalanine given but also the blood tyrosine level.
口服苯丙氨酸负荷会导致苯丙酮尿症患儿血清酪氨酸水平显著下降[8]。本研究的目的是检测胰岛素和胰高血糖素对口服苯丙氨酸负荷的反应，因为已知这些激素具有降低氨基酸血症的作用。6名体重正常且健康的成年男性在禁食过夜后，按每千克体重口服0.6 mmol的L-苯丙氨酸。负荷后10分钟内血清苯丙氨酸升高，并在30分钟时达到最高浓度。负荷后10分钟内血清酪氨酸升高，并在2小时时达到最高浓度。血浆胰高血糖素和胰岛素在负荷后的前10分钟内升高，并在负荷后30分钟时达到空腹水平两倍的峰值。胰岛素/胰高血糖素摩尔比在负荷后的前20分钟内保持不变，但在2小时时下降了50%。与此下降相关，血浆氨基酸浓度（苯丙氨酸和酪氨酸除外）下降了约15%。异亮氨酸、亮氨酸、蛋氨酸和缬氨酸的下降最为明显。由于已知胰岛素和胰高血糖素的降低氨基酸血症作用对这四种氨基酸以及苯丙氨酸和酪氨酸最为显著，胰岛素和胰高血糖素对苯丙氨酸负荷的反应可能不仅会影响所给予苯丙氨酸的命运，还会影响血液酪氨酸水平。
