Detection of Urinary Epithelial Sodium Channel (ENaC) Protein

Epithelial sodium Channel (ENaC) protein is an important substance in maintaining plasma sodium level. Its DNA sequences are similar in rat model with and without salt sensitivity, but the mRNA number increase in salt sensitive rat model with high salt diet. This condition is assumed to be similar in human. ENaC protein is abundant in lung, gut and kidney, and plays a similar physiological process but different diseases. ENaC protein levels have to be measured from specific locations; kidney will be the good source for hypertension related sodium excretion. The possibility of ENaC protein as a marker to screen salt-sensitivity is needed to be explored. The aim of this research is to explore the possibility of ENaC protein detection in urine. This is an observational descriptive study. Enzyme-linked immunosorbent assay (ELISA), using Cloud-Clone reagent catalog number SED337Hu, was used to detect and measure urinary and plasma ENaC protein level. For the first step of study, ELISA was conducted toward various dilution of healthy individual spot urine; in the 2nd step, several locations of repeated centrifuged spot urine and 24 hour collected urine were explored for the presence of ENaC protein; on the next step, 3 subjects, non-hypertensive, and hypertensive with and without family history of hypertension were recruited; for the fourth step, 13 (6 male and 7 female) non-hypertensive subjects were recruited; all steps are aimed to explore the detection of urinary EnaC protein level. ENaC proteins can be detected in both supernatant and sediment of centrifuged urine. In plasma of non-hypertensive, hypertensive with, and without family history of hypertension are 1.12 ng/ml, 2.7 ng/ml and 4.0 ng/mL respectively. ENaC protein levels from centrifuged urine at lower part of supernatant are lower but consistent with serum level. Mean ENaC protein level in non-hypertensive men are lower than women. Mean ENaC protein level in those with family history of hypertension are lower both in men and women. ENaC protein is detectable in spot urine; the levels differ by hypertension status, family history of hypertension and also by gender.