PS-BPB10-2: MOLECULAR INSIGHT INTO SALT-SENSITIVITY; THE ROLE OF ATF3 AND THE GENERATION OF TUBULAR SPECIFIC KO MICE. (1)

Abstract

Objectives: Current research including ours suggested pivotal roles of expressions of and regulations of tubular ion transporters for developments of sodium sensitivity and hypertension. Orlov et al. demonstrated using rat cardiomyocytes three different genes which are activated according to the elevation of intra-cellular Na ion concentration. (2015) To elucidate detailed biological roles of these genes in tubules, we performed current experiments. Methods: We tested expressions of three genes for cDNA from kidneys of Nedd4 2 C2 KO mice using quantitative RT PCR methods. Subsequently, we performed crossbreeding experiments between floxed target gene mice (generous gift from Prof. Kitamura, Tokyo Medical and Dental University) and Ksp-cre mice (Jackson Laboratory), which cre-recombinase expresses specifically along urinary tubules to generate mice with cre+, flox/flox genotype. Results: We found expressions of Atf3 are significantly changed due to oral sodium intake and diuretics treatment in Nedd4–2 C2 KO mice. We successfully generated mice with cre+, Atf3 flox/flox mice for current experiments. Under normal salt diet, we could not find any significant differences between cre + and minus mice in terms of systolic blood pressure, water intake, urine volume, urinary sodium excretions, urinary pH, and urinary osmotic pressures using metabolic cage experiments. We found, under high salt intake, gene expressions of both classic renin and tubular alternative renin are significantly suppressed for 30 to 70% in KO mice by quantitative RT PCR and immunohistochemistry imaging. Conclusions: Tubular epithelial Atf3 genes are involved in regulations of renin gene expressions in accordance with intracellular Na ion concentrations. Therefore, there are possibilities that tubular specific Atf3 KO mice shows blood pressure change under various salt intake and diuretics treatment.