Dantzler W H, Silbernagl S
Pflugers Arch. 1976 Dec 28;367(2):123-8. doi: 10.1007/BF00585147.
Renal tubular reabsorption of taurine, gamma-aminobutyric acid (GABA), and beta-alanine was studied in vivo et situ by continuous microperfusion of single proximal tubules of the rat. In each case, reabsorption was much slower than that for other amino acids that have been studied. With a concentration of 0.1 mmol/l in initial load was reabsorbed over perfusion distance of 3 mm. Taurine reabsorption saturated with only 2.17 mmol/l in initial perfusate. Assuming simple two-parameter kinetics, upper limits for Km of 0.54 mmol/l and forVmax of 0.59 pmol-cm-1--s-1 for tubular reabsorption of taurine were estimated. High (20 mmol/l) concentrations of taurine or beta-alanine in perfusate completely inhibited GABA reabsorption, but L-phenylalanine (20 mmol/l) had no significant effect. The results indicate that the three amino acids are reabsorbed slowly from the proximal tubule by what may be a common transport system. This system appears to have a high affinity but low capacity and to be different from other known renal tubular transport systems for amino acids.
通过对大鼠单个近端肾小管进行连续微灌注,在体内原位研究了牛磺酸、γ-氨基丁酸(GABA)和β-丙氨酸的肾小管重吸收。在每种情况下,重吸收都比已研究的其他氨基酸慢得多。初始负荷浓度为0.1 mmol/l时,在3 mm的灌注距离内被重吸收。初始灌注液中牛磺酸重吸收仅在2.17 mmol/l时达到饱和。假设为简单的双参数动力学,估计牛磺酸肾小管重吸收的Km上限为0.54 mmol/l,Vmax上限为0.59 pmol·cm⁻¹·s⁻¹。灌注液中高浓度(20 mmol/l)的牛磺酸或β-丙氨酸完全抑制GABA重吸收,但L-苯丙氨酸(20 mmol/l)无显著影响。结果表明,这三种氨基酸可能通过一种共同的转运系统从近端肾小管缓慢重吸收。该系统似乎具有高亲和力但低容量,且不同于其他已知的肾小管氨基酸转运系统。