Bouby N, Coutaud C, Bankir L
INSERM U 90, Hôpital Necker, Paris, France.
Miner Electrolyte Metab. 1992;18(2-5):101-3.
The high plasma level of citrulline (Cit) is one of a number of abnormalities in the plasma amino acid pattern in chronic renal failure (CRF). Synthesis of arginine (Arg) from citrulline in the kidney is the major source of Arg for the body. In order to evaluate the renal activity of Arg synthesis in CRF, we studied arginine production in proximal convoluted tubules (PCT) isolated from male Sprague-Dawley rats 1 month after 5/6 nephrectomy and from sham-operated rats (n = 6 of each). PCT segments were incubated in a sealed chamber with 50 or 200 microM of [L-ureido 14C]-Cit (simulating in vivo plasma concentrations in healthy rats or rats with CRF, respectively). Arginase and urease were added to the medium to hydrolyze Arg into 14CO2 + NH3. 14CO2 was trapped in KOH and counted. Results showed that: (1) in CRF, Arg production per unit tubular length is increased in proportion to hypertrophy of PCT (x 1.5); (2) in CRF, as in the healthy kidney, Arg production increases with Cit concentration (x 2.5 from Cit 50 to 200 microM). Taking into account the hypertrophy and the elevation in Cit concentration, the increase in Arg production per unit length (x 3.6) is not sufficient to compensate for the reduction in nephron number. Most likely, a greater length of maximal tubule is recruited for renal Arg synthesis in CRF.
慢性肾衰竭（CRF）患者血浆中瓜氨酸（Cit）水平升高是血浆氨基酸谱异常之一。肾脏中由瓜氨酸合成精氨酸（Arg）是机体Arg的主要来源。为了评估CRF患者肾脏中Arg合成活性，我们研究了5/6肾切除术后1个月的雄性Sprague-Dawley大鼠及假手术大鼠（每组n = 6）分离出的近端小管（PCT）中精氨酸的生成情况。PCT节段在密封室中与50或200 μM的[L-脲基14C]-瓜氨酸（分别模拟健康大鼠或CRF大鼠的体内血浆浓度）一起孵育。向培养基中加入精氨酸酶和脲酶，将Arg水解为14CO2 + NH3。14CO2用KOH捕获并计数。结果显示：（1）在CRF中，单位肾小管长度的Arg生成量与PCT肥大程度成比例增加（增加1.5倍）；（2）在CRF中，与健康肾脏一样，Arg生成量随瓜氨酸浓度增加（从50 μM瓜氨酸增加到200 μM时增加2.5倍）。考虑到肥大和瓜氨酸浓度升高，单位长度Arg生成量的增加（增加3.6倍）不足以弥补肾单位数量的减少。很可能，CRF中肾脏Arg合成募集了更长的最大肾小管长度。
