Genomic regulation of intestinal amino acid transporters by aldosterone

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Abstract

Overexpression of renal LAT2, a Na+-independent L-amino acid transporter, in spontaneous hypertensive rats (SHR) is organ specific and precedes the onset of hypertension (Pinho et al., Hypertension, 42:613–618, 2003). However, the expression of LAT2 correlates negatively with plasma aldosterone levels after high sodium intake (Pinho et al., Am J Physiol Ren Physiol 292:F1452–F1463, 2007). The present study evaluated the expression of Na+-independent LAT1, LAT2, and 4F2hc and Na+-dependent ASCT2 amino acid transporters in the intestine of normotensive Wistar rats chronically treated with aldosterone. In conditions of high salt intake, to keep endogenous aldosterone to a minimum, rats were implanted with aldosterone or spironolactone tablets. In aldosterone-treated and aldosterone + spironolactone-treated rats, aldosterone plasma levels were increased by fourfold. At the protein level, aldosterone treatment significantly increased LAT1 (62%), LAT2 (49%), 4F2hc (48%), and ASCT2 (65%) expression. The effect of aldosterone upon LAT1, LAT2, 4F2hc, and ASCT2 protein abundance was completely reversed by spironolactone. Aldosterone significantly increased intestinal LAT2 and 4F2hc mRNA levels (27% and 35% increase, respectively), with no changes in LAT1 and ASCT2 transcript levels. In conclusion, increases in intestinal Na+-independent LAT1 and LAT2 and Na+-dependent ASCT2 transcript and protein abundance during chronic treatment with aldosterone occur through a spironolactone-sensitive genomic mechanism.

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