title: Effects of thyroid hormone on the neonatal renal cortical Na+/H+ antiporter.
abstract: 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.
authors.affiliation: Department of Pediatrics, University of Texas Southwestern Medical Center, Dallas, USA. mbaum@mednet.swmed.edu
authors.forename: M
authors.initials: M
authors.lastname: Baum
authors.forename: V
authors.initials: V
authors.lastname: Dwarakanath
authors.forename: R J
authors.initials: RJ
authors.lastname: Alpern
authors.forename: O W
authors.initials: OW
authors.lastname: Moe
mesh_terms: D000818:Animals; D000831:Animals, Newborn; D013956:Antithyroid Agents / Q000633:toxicity; D005260:Female; D006980:Hyperthyroidism / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D007037:Hypothyroidism / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism; D007672:Kidney Cortex / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000187:drug effects / Q000378:metabolism; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D011441:Propylthiouracil / Q000633:toxicity; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D014284:Triiodothyronine / Q000494:pharmacology*
chemical_list: D013956:Antithyroid Agents; D012333:RNA, Messenger; C000613387:Slc9a3 protein, rat; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; D014284:Triiodothyronine; D011441:Propylthiouracil; D000254:Sodium-Potassium-Exchanging ATPase