The purpose of the present study was to examine whether
metabolic acidosis affects the expression of rat renal Na(+)/
citrate cotransporter. Female Wistar rats were pair-fed with normal rat chow and
drinking water (control) or water with 0.28 mol/L NH4Cl (
metabolic acidosis). The
mRNA of two renal Na(+)/
citrate cotransporters, which were respectively expressed on apical and basolateral membrane, were measured by Northern blot with two probes, SDCT1 and
SDCT2. Animals were sacrificed on day 1,3 and 7. On the 1st day, the blood plasma HCO(-)3 of
acidosis group decreased significantly (P<0.01), but the
mRNA abundance did not change. On the 3rd day in the
acidosis group, the blood plasma HCO(-)3 increased slightly more than that on the 1st day, but was still significantly lower than that of the control group (P<0.01). Both the probes detected some increase in
mRNA of brush border and basolateral Na(+)/
citrate cotransporter. On the 7th day, the blood plasma HCO(-)3 of the
acidosis group continuously increased and there was no significant difference between the two groups. The abundance of brush border and basolateral Na(+)/
citrate cotransporter
mRNA increased, but there was no difference between those of the 3rd day and the 7th day. It is concluded that
metabolic acidosis can induce increase of Na(+)/
citrate cotransporter
mRNA, which may be responsible for hypocitraturia.