Effect of Lowered Aldosterone Levels on the Expression of Mineralocorticoid Receptors in Normal and Hypertensive Rat Kidneys

Hypertension is a major health concern among adults worldwide that can lead to cardiac morbidity or death. One cause of hypertension stems from the relationship between the binding of aldosterone and active glucocorticoids to the mineralocorticoid receptor (MR). Aldosterone or active glucocorticoid hormones bind to the MR; this event signals the synthesis of proteins that cause hypertension. Previous results have shown that cryodestruction of ^e adrenal gland outer layer reduced the levels of aldosterone, but did not always lower blood pressure in the mothers or progeny. These data could have resulted from a compensating increase in the binding by active glucocorticoids or from an increase in the expression of MR. In order to test the latter hypothesis, the levels of the MR were measured in control rat kidney tissues and treated rat kidney tissues. RNA was isolated and quantified from the kidney tissue and then reverse transcribed. Primers and labeled probes were designed for an exon junction region in the MR cDNA and for an exon junction region in a housekeeping cDNA. A real time polymerase chain reaction method was optimized to measure the levels of mineralocorticoid RNA . Then this method was applied to assess differences between the cryotreated tissues and between normal and hypertensive rat kidney tissues