title: Calcium and magnesium transport in the cortical thick ascending limb of Henle's loop: influence of age and gender.
abstract: Previous studies from our laboratory have shown that Ca2+ and Mg2+ absorption in the mouse cortical thick ascending limb of Henle's loop (cTAL) is a passive, paracellular process driven by the transepithelial voltage. The passive permeability of the epithelium is enhanced by peptide hormones. The present study investigated whether divalent cation absorption in the cTAL is influenced by cell maturation and/or gender. For this purpose, mouse cTAL segments were microdissected from kidneys of female and male animals aged 4 and 8 weeks. The microdissected tubules were perfused in vitro at a luminal flow rate of 1.5 to 2.5 nl/min. Transepithelial Na+, Cl-, Ca2+ and Mg2+ net fluxes (JX, pmol.min-1.mm-1) were measured using electron microprobe analysis, and the transepithelial potential difference (PDte) was measured continuously. No differences were found in the PDte, JNa and JCl of the various animal groups but the transepithelial Ca2+ and Mg2+ transport capacity of the cTAL was higher in adults (8 weeks) than in young animals (4 weeks). Furthermore, irrespective of age, transepithelial Ca2+ net absorption was greater in male than in female animals. In contrast, the NaCl transport was maximal at 4 weeks in both genders. We conclude therefore that transepithelial divalent cation absorption in the mouse cTAL is an inductive process influenced by cell maturation and gender. The molecular basis of these inductions remains to be elucidated.
authors.affiliation: Cattedra di Nefrologia, Dipartimento di Pediatria, Seconda Universita' degli Studi di Napoli, I-80131 Naples, Italy.
authors.forename: M
authors.initials: M
authors.lastname: Wittner
authors.forename: E
authors.initials: E
authors.lastname: Desfleurs
authors.forename: S
authors.initials: S
authors.lastname: Pajaud
authors.forename: G
authors.initials: G
authors.lastname: Moine
authors.forename: S
authors.initials: S
authors.lastname: Simeone
authors.forename: C
authors.initials: C
authors.lastname: de Rouffignac
authors.forename: A
authors.initials: A
authors.lastname: Di Stefano
mesh_terms: D000042:Absorption; D000818:Animals; D001692:Biological Transport; D002118:Calcium / Q000493:pharmacokinetics*; D016922:Cellular Senescence / Q000502:physiology; D005260:Female; D066298:In Vitro Techniques; D007672:Kidney Cortex; D008138:Loop of Henle / Q000166:cytology / Q000378:metabolism*; D008274:Magnesium / Q000493:pharmacokinetics*; D008297:Male; D051379:Mice; D012727:Sex Characteristics
chemical_list: D008274:Magnesium; D002118:Calcium