Developmental Aspects of Renal β-Amino Acid Transport I. Ontogeny of Taurine Reabsorption and Accumulation in Rat Renal Cortex
Developmental Aspects of Renal β-Amino Acid Transport I. Ontogeny of Taurine Reabsorption and Accumulation in Rat Renal Cortex
复制标题
肾 β-氨基酸转运的发育方面 I. 大鼠肾皮质牛磺酸重吸收和积累的个体发育
作者：
R. Chesney;D. K. Jax
摘要：研究发现，新生的Sprague-Dawley大鼠幼崽体内β-氨基酸牛磺酸的净管回收量减少。该化合物的重吸收在出生后的第2周和第4周之间增加，尽管肾小球滤过率上升表明随着成熟转运增加，但排泄的牛磺酸减少。肾皮质在体内从血浆中积累牛磺酸，具有很大的化学梯度。新生儿皮质片在<0.4 mM的稳定状态下积累了较高水平的牛磺酸，但在较高的牛磺酸浓度下吸收效率较低。皮质切片对牛磺酸的进一步代谢在任何年龄均未发现。在10-15 mEq/l K的外部培养基中，成人和新生儿皮层的积累量最大。幼龄动物的肾脏切片具有稍高的摄取最佳pH值，并且温度升高使新生儿肾脏的摄取比成人肾脏的摄取更多。推测：如果新生大鼠部分依赖牛磺酸通过乳汁从母亲转移到幼鼠，那么断奶过程可能需要更大的肾小管重吸收，以维持组织和血浆中的牛磺酸池。在4周龄和成年动物中发现的牛磺酸重吸收的改善可能反映了断奶后饲料中牛磺酸（和其他含硫氨基酸）的减少所带来的成熟变化。
Summary: Newborn Sprague-Dawley rat pups were found to have reduced net tubular reclamation of the β-amino acid taurine in vivo. The reabsorption of this compound increased between the 2nd and 4th week of life and the excreted taurine fell despite a rise in glomerular filtration rate indicative of increased transport with maturation.Kidney cortex in vivo accumulated taurine from plasma against a large chemical gradient. Newborn cortex slices in vitro accumulated taurine to higher levels at steady state at <0.4 mM, but uptake was less efficient at higher taurine concentrations. Further metabolism of taurine by cortex slices was not found at any age. Accumulation in adult and newborn cortex was greatest at 10–15 mEq/liter K in the external medium. Slices from younger animals had slightly higher pH optima for uptake and temperature elevation increases uptake more in neonatal than in adult kidney.Speculation: If the newborn rat is in part dependent on the transfer of taurine from mother to pup via milk, the process of weaning may require greater renal tubular reabsorption in order to maintain tissue and plasma pools of taurine. The improved reabsorption of taurine found in 4-week-old and adult animals may reflect maturational changes brought about by the reduction in dietary taurine (and other sulfur containing amino acids) after weaning.