AJP - Renal Physiology, Vol 265, Issue 6 807-F812, Copyright © 1993 by American Physiological Society
Effect of fetal exposure to gentamicin on phosphate transport in young rat kidney
M. Lelievre-Pegorier, S. Euzet and C. Merlet-Benichou
Unite de Recherches sur le Developpement Normal et Pathologique des Fonctions Epitheliales, Institut National de la Sante et de la Recherche Medicale Unite 319, Universite Paris 7, France.
The renal phosphate (Pi)-transporting capacity normally increases, due to
increased carrier system affinity, during the third postnatal week in rats.
However, the tubular Pi reabsorption of rat pups born from
gentamicin-treated mothers does not increase during this period. This study
determines whether exposure to gentamicin in utero selectively alters the
postnatal maturation of the carrier affinity for Pi. Pi and glucose
transports by proximal tubule brush-border membrane (BBM) were studied. The
maximal rate of uptake (Vmax) of Na-Pi cotransport was significantly lower
(536 +/- 169 pmol.mg protein-1.10 s-1; n = 6, P < 0.01) in
gentamicin-exposed rats than in controls (1,021 +/- 167 pmol.mg
protein-1.10 s-1, n = 6), whereas the Michaelis constant (Km) values were
the same. Gentamicin exposure had no effect on plasma parathyroid hormone
concentration or on BBM glucose transport activity. The total phospholipid
content of BBM, their phospholipid composition, cholesterol content, and
cholesterol-to-total phospholipid mole ratio were unaltered, suggesting
that membrane fluidity was unchanged. The Vmax of BBM alkaline phosphatase
was lower in gentamicin-exposed rats than in controls.
