AJP - Renal Physiology, Vol 249, Issue 1 74-F83, Copyright © 1985 by American Physiological Society
Phosphate uptake by proximal cells isolated from rabbit kidney: role of dexamethasone
P. Poujeol and A. Vandewalle
A single cell suspension was prepared from rabbit kidney cortex by gentle
mechanical dissociation. The isolated cells were functionally intact and
metabolically active, as indicated by exclusion of eosin dye, respiratory
measurement, and ATP content. The isolated cells were shown to possess long
microvilli, and their proximal origin was confirmed by enzymatic and
glucose production studies. The uptakes of 0.1 mM phosphate (Pi) and 0.05
mM D-glucose at 37 degrees C were strongly dependent on the extracellular
Na+. Incubation of the cells with parathyroid hormone (10 U/ml) for 20 min
reduced 20-s Pi uptake by 20%. The addition of dibutyryl cAMP decreased Pi
uptake, with a maximal effect at 10(-6) M. Incubation of cells with
gluconeogenic substrates, under conditions in which glucose production was
increased, did not promote any change in Pi accumulation. When incubated
for 60 min at 37 degrees C in the presence of dexamethasone (Dex), the
Na+-dependent Pi uptake was decreased by 29% at 10(-9) M and by 36% at
10(-7) M without modification of the glucose uptake. Replacing Dex by
aldosterone (10(-7) M) remained without effect on Pi uptake. It is
concluded that: renal cells isolated by our preparative method are mainly
of proximal origin; isolated cells are a good model for studying the
regulation of Pi uptake in the proximal tubule; and glucocorticoids have an
acute specific effect on Pi transport detectable in vitro and this effect
does not seem to be related to modifications of renal gluconeogenesis.
