Pena D R, Neiberger R E
Department of Pediatrics, JHMHC, University of Florida College of Medicine, Gainesville 32610-0296.
Pediatr Nephrol. 1992 Nov;6(6):532-5. doi: 10.1007/BF00866495.
Renal tubular reabsorption of inorganic sulfate is greater in younger than older guinea pigs. To determine the mechanism of this difference, we studied the transport of inorganic sulfate in renal brush border membrane vesicles (BBMV) obtained from young (< 25 days) and adult guinea pigs (> 60 days). BBMV were obtained by mechanical and osmotic disruption of dissected renal cortices followed by magnesium precipitation and differential centrifugation. After the membranes were incubated for 10 s in solutions containing inorganic sulfate at several concentrations (0.1-10 mM) and trace amounts of 35sulfate, intravesicular uptake was measured. Based on 35sulfur uptake, reabsorption transport kinetics (Vmax and Km) were estimated. BBMV obtained from young guinea pigs demonstrated higher sodium-sulfate cotransport, Vmax (51.79 +/- 4.34 pmol/mg protein per s) than those obtained from adult animals (Vmax = 34.28 +/- 9.17 pmol/mg per s), P < 0.05. Vmax values are represented as means plus or minus standard deviation. No differences in Km were observed. Our results indicate that age-related differences in renal inorganic sulfate reabsorption are due to a higher Vmax for sodium-sulfate cotransport in the younger animals, suggesting a higher density of sodium-sulfate cotransporters or an increased cotransport turnover rate in this age group.
幼年豚鼠肾小管对无机硫酸盐的重吸收能力强于成年豚鼠。为了确定这种差异的机制，我们研究了从幼年（<25天）和成年豚鼠（>60天）获得的肾刷状缘膜囊泡（BBMV）中无机硫酸盐的转运情况。通过对解剖后的肾皮质进行机械和渗透破坏，然后进行镁沉淀和差速离心来获得BBMV。将膜在含有几种浓度（0.1 - 10 mM）无机硫酸盐和微量35硫酸盐的溶液中孵育10秒后，测量囊泡内摄取量。基于35硫摄取量，估算重吸收转运动力学（Vmax和Km）。从幼年豚鼠获得的BBMV显示出比成年动物更高的钠 - 硫酸盐共转运Vmax（51.79 +/- 4.34 pmol/mg蛋白质每秒）（成年动物Vmax = 34.28 +/- 9.17 pmol/mg每秒），P < 0.05。Vmax值表示为平均值加减标准差。未观察到Km有差异。我们的结果表明，肾无机硫酸盐重吸收的年龄相关差异是由于幼年动物中钠 - 硫酸盐共转运的Vmax较高，这表明该年龄组中钠 - 硫酸盐共转运体的密度较高或共转运周转率增加。
