title: Ontogeny of cortical collecting duct sodium transport.
abstract: The postnatal maturation of Na transport in the rabbit cortical collecting duct (CCD) was investigated. CCD segments from rabbits of three different age groups (3-9 days, 10-15 days, and 22-27 days) were perfused in vitro. Lumen-to-bath 22Na fluxes were 38.5 +/- 4.7, 17.0 +/- 2.9, and 30.2 +/- 4.0 pmol.mm-1.min-1 in the three groups, respectively. The high flux in the youngest group was explained by a high passive flux (28.3 +/- 4.2 pmol.mm-1.min-1) determined in the presence of ouabain; the passive 22Na flux in the two other groups (7.1 +/- 2.6 and 3.1 +/- 2.4 pmol.mm-1.min-1) was not significantly different from previously reported adult values. Ouabain-sensitive 22Na flux, reflecting active transport, was low in the two younger groups (10.3 +/- 2.5 and 9.9 +/- 1.9 pmol.mm-1.min-1), but exhibited a rapid increase to 27.1 +/- 2.6 pmol.mm-1.min-1 by 22-27 days of age. In vivo glucocorticoid pretreatment did not affect the Na transport in any age group. Mineralocorticoid pretreatment for 2 days had no effect in the two younger groups, but increased lumen-to-bath 22Na flux from 30.2 +/- 4.0 to 51.1 +/- 4.3 pmol.mm-1.min-1 in the 22- to 27-day-old group. The findings demonstrate that the maturation of rabbit CCD Na transport occurs in two stages, with the first consisting of a decrease in passive permeability during the first 2 wk of life, followed by an increase in active transport and simultaneous development of mineralocorticoid responsiveness.
authors.affiliation: Department of Pediatrics, Washington University School of Medicine, St. Louis, Missouri 63110.
authors.forename: V M
authors.initials: VM
authors.lastname: Vehaskari
mesh_terms: D000375:Aging / Q000378:metabolism*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D003900:Desoxycorticosterone / Q000494:pharmacology; D003907:Dexamethasone / Q000494:pharmacology; D066298:In Vitro Techniques; D007672:Kidney Cortex; D007685:Kidney Tubules, Collecting / Q000254:growth & development* / Q000378:metabolism*; D010042:Ouabain / Q000494:pharmacology; D010477:Perfusion; D011817:Rabbits; D012964:Sodium / Q000378:metabolism*
chemical_list: D003900:Desoxycorticosterone; D010042:Ouabain; D003907:Dexamethasone; D012964:Sodium