Levillain O, Hus-Citharel A, Morel F, Bankir L
INSERM, Unité 90, Hôpital Necker, Paris, France.
Ren Physiol Biochem. 1989 Sep-Dec;12(5-6):302-12. doi: 10.1159/000173207.
Urea production from arginine was studied in vitro in the kidney of normal rats in tubule suspensions of the four different renal zones (cortex, outer and inner stripe of outer medulla, and inner medulla), and in individual microdissected nephron segments. Tissue was incubated with L-[guanido-14C]-arginine to measure cellular arginase activity. Addition of urease to the incubate freed 14CO2 from the 14C-urea formed by arginase and released from the cells. CO2 was trapped in KOH and counted. These experiments revealed that significant amounts of urea are produced in the outer stripe and in the inner medulla. This intrarenal urea generation takes place mainly in the proximal straight tubule and in the collecting duct, with increasing activity in these two structures from superficial to deep regions of the kidney. Urea is known to play a critical role in the urinary concentrating process. The fact that some urea can be produced in the mammalian kidney, and that the two structures showing this capacity are straight portions of the renal tubular system descending along the corticopapillary axis suggest that this urea production might play a role in the formation and/or maintenance of the medullary urea concentration gradient.
在体外研究了正常大鼠肾脏中从精氨酸生成尿素的情况，实验对象包括四个不同肾区（皮质、外髓质外带和内带以及内髓质）的肾小管悬浮液，以及单个经显微解剖的肾单位节段。将组织与L-[胍基-¹⁴C]-精氨酸一起孵育，以测量细胞精氨酸酶活性。向孵育液中添加脲酶可使精氨酸酶形成并从细胞中释放出的¹⁴C-尿素释放出¹⁴CO₂。CO₂被捕获在KOH中并进行计数。这些实验表明，在外带和内髓质中会产生大量尿素。这种肾内尿素生成主要发生在近端直小管和集合管，并且在这两个结构中，从肾脏的浅部到深部区域，活性逐渐增加。已知尿素在尿液浓缩过程中起关键作用。哺乳动物肾脏中能够生成一些尿素，且具有这种能力的两个结构是沿皮质-乳头轴下行的肾小管系统的直部，这一事实表明这种尿素生成可能在髓质尿素浓度梯度的形成和/或维持中发挥作用。
