AJP - Cell Physiology, Vol 263, Issue 1 C61-C68, Copyright © 1992 by American Physiological Society
Time course of sodium-induced Na(+)-K(+)-ATPase recruitment in rabbit cortical collecting tubule
N. Coutry, M. Blot-Chabaud, P. Mateo, J. P. Bonvalet and N. Farman
Institut National de la Sante et de la Recherche Medicale Unite 246, Paris, France.
In cortical collecting tubules (CCD) of aldosterone-repleted rabbit kidney,
an increase in intracellular sodium concentration (Nai) induces the
recruitment and/or activation of latent Na(+)-K(+)-ATPase pumps
(Blot-Chabaud et al., J. Biol. Chem. 265: 11676-11681, 1990). The present
study was addressed to determine the time course of this Nai-dependent pump
recruitment and to examine some of the factors possibly involved in this
phenomenon. CCD from adrenalectomized rabbits complemented with aldosterone
and dexamethasone were incubated at 4 degrees C either in a K(+)-free
saline solution (Na(+)-loaded CCD) or in a sucrose solution (control CCD)
and then rewarmed for various time periods to allow pump recruitment to
occur. The number of pumps in the membrane was determined by specific
[3H]ouabain binding; Nai was measured using 22Na. A rise in Nai induced a
threefold increase in the number of basolateral pumps, which was fully
achieved within 1-2 min. This pump recruitment was reversible within 15 min
after restoration of low Nai. It was unaffected by inhibitors of
cytoskeleton and Ca2+ ionophore A 23187. The blocker of the Na(+)-H+
antiporter, amiloride, did not prevent it. The protein kinase C activator,
phorbol 12-myristate 13-acetate, did not induce it in the absence of Na+.
We conclude that Nai is a major determinant of pump recruitment and/or
activation, which occurs over a very short period of time. It may
constitute a rapid adaptative response to an increase in the cell Na+ load.
