The Effect of Maternal Aldosterone Levels on the Expression of 11B-HSD Isoenzymes in Normal and Hypertensive Rat Placentae

Abstract

In this project, we developed a Western blotting procedure to semi-quantitate levels of 11β-HSD1 and 11β-HSD2 in whole cell extracts. Then, we applied this technique to analyze the effect of reduced maternal aldosterone levels on the expression of 11β-HSD1 and 11β-HSD2 isoenzymes in the placental tissue in both normal and hypertensive rats. These enzymes control levels of glucocorticoids which compete for aldosterone’s mineralocorticoid receptor. Overstimulation of this receptor results in hypertension. If aldosterone levels decrease, levels of the enzymes controlling active glucocorticoid concentrations might change to compensate for the lowered aldosterone levels. Decreased placental 11β-HSD2 expression could affect hypertension in the offspring. The Western blotting procedure was optimized for the detection of the two isoenzymes in their dimeric forms. The use of multiple protein levels on the blot was useful to obtain a more reliable semi-quantitation. Because of the presence of multiple bands, it was impossible to use an internal beta actin standard to normalize the data from one blot to another. This along with the low expression levels and uneven blot backgrounds made it difficult to obtain enough data on the expression of the two isoenzymes. Very limited data do not support differences in the placental expression of the two isoenzymes when maternal aldosterone levels are lowered