The Effect of Lowered Aldosterone on the Expression of Mineralocorticoid Receptor Isoforms α, β and γ

Aldosterone is a hormone secreted by the adrenal gland that binds to cytoplasmic mineralocorticoid receptors (MR). The binding of this hormone to its receptor increases the synthesis of the epithelial sodium channel (ENaC) and Na+/K+ATPase proteins which control the passage of sodium and potassium ions, Mineraolcorticoid receptors exist in three isoform structures called alpha, beta, and gamma. Lowering of aldosterone levels can affect blood pressure and hypertension. The objective of this research was to develop three qPCR (quantitative polymerase chain) methods to measure the expression of the three MR isoforms in rat kidneys. The second objective was to test whether lowered aldosterone levels changed the expression of these MR isoforms in the kidneys of treated rats or their male offspring. Total RNA was isolated and reverse transcription was used to make the copy DNAs. Software was used to design TaqMan primers and probes over exon junctions with unique sequences for each isoform, It was found that that the expression of the alpha isoform may be slightly lower in normotensive rat kidneys and in the offspring of spontaneously hypertensive rat kidneys of mothers who had been treated to lower aldosterone levels. More samples need to be run to verify this trend and to establish significance. MR γ displayed no differences among the kidney samples and the MR β assay was not efficient enough to pursue expression analyses.