Baum M, Dwarakanath V, Alpern R J, Moe O W
Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, USA.
Kidney Int. 1998 May;53(5):1254-8. doi: 10.1046/j.1523-1755.1998.00879.x.
The neonatal proximal tubule has a lower rate of bicarbonate absorption than that of adults. This is due, in part, to a lower rate of apical membrane Na+/H+ antiporter activity. The purpose of these studies was to examine if thyroid hormone could be a factor in the maturational increase in Na+/H+ antiporter activity. Hypothyroid (0.01% propylthiouracil in drinking water starting at day 14 gestation and throughout the postnatal period), euthyroid, and hyperthyroid (intraperitoneal triiodothyronine, 10 micrograms/100 g body wt, once daily on days 17 to 20 of postnatal life) rats were all studied at 21 days of life. Renal cortical brush border Na+/H+ antiporter activity was 453 +/- 24, 527 +/- 30 and 608 +/- 25 pmol/mg protein in the hypothyroid, euthyroid and hyperthyroid groups, respectively (P < 0.001). Hyperthyroid neonates had approximately twofold greater renal cortical NHE-3 mRNA abundance than euthyroid and hypothyroid neonates (P < 0.05). Brush border membrane NHE-3 protein abundance in hypothyroid and hyperthyroid neonates was one-third and twofold that of euthyroid 21-day-old rats, respectively (P < 0.001). These data are consistent with a potential role of thyroid hormone in the postnatal increase in Na+/H+ antiporter activity.
新生大鼠近端肾小管对碳酸氢盐的重吸收率低于成年大鼠。部分原因是顶端膜钠氢交换体活性较低。这些研究的目的是检验甲状腺激素是否可能是钠氢交换体活性成熟性增加的一个因素。研究了甲状腺功能减退（从妊娠第14天开始并在整个出生后时期，饮用水中含0.01%丙硫氧嘧啶）、甲状腺功能正常和甲状腺功能亢进（出生后第17至20天，腹腔注射三碘甲状腺原氨酸，10微克/100克体重，每日一次）的大鼠，均在出生后21天进行研究。甲状腺功能减退组、甲状腺功能正常组和甲状腺功能亢进组肾皮质刷状缘钠氢交换体活性分别为453±24、527±30和608±25皮摩尔/毫克蛋白（P<0.001）。甲状腺功能亢进的新生大鼠肾皮质NHE-3 mRNA丰度比甲状腺功能正常和甲状腺功能减退的新生大鼠高约两倍（P<0.05）。甲状腺功能减退和甲状腺功能亢进新生大鼠的刷状缘膜NHE-3蛋白丰度分别是甲状腺功能正常的21日龄大鼠的三分之一和两倍（P<0.001）。这些数据与甲状腺激素在出生后钠氢交换体活性增加中可能发挥的作用一致。
