Establishment of a mutagenesis screen to identify mice with high aldosterone levels.

According to recent epidemiological studies, primary aldosteronism is considered to be responsible for almost 10% of all cases of arterial hypertension. The genetic background of this common disease, however, has been elucidated only for the rare familial types whereas in the large majority of sporadic cases it still remains unclear. In an attempt to define novel genetic mechanisms of hyperaldosteronism we utilized a random mutagenesis screen after treatment with the alkylating agent N-ethylnitrosourea (ENU) and phenotypically characterized affected mice for their blood aldosterone levels. As the detection method we used a time resolved fluorescent immunoassay which allows the measurement of aldosterone in very small murine plasma volumes. Using this assay we determined the normal aldosterone values for C3H wild type mice under baseline conditions (mean ± 3 standard deviations (SD): 92±53 pg/ml for female [n=69] and 173±114 pg/ml for male [n=55] mice) and following specific stimulation and suppression tests. Subsequently, aldosterone measurement was carried out in more than 2000 F1 offspring (of both genders) of chemically mutated inbred C3H mice. Out of these F1 offspring tested, aldosterone levels were consistently elevated (defined as levels above 3 SD over the mean of untreated animals) upon repeated measurement in 7 female animals (456±104 pg/ml at initial time point). So far, no affected male mice could be identified in the F1 generation. Further breeding of affected female animals gave rise to F2 pedigrees from which two established lines display high aldosterone values in 50% of their littermates as would be expected from an autosomal dominant trait of inheritance. These animals will serve for detailed phenotypic characterization and furthermore genetic SNP analysis in the future. Taken together our data demonstrate the feasibility of a phenotype-driven mutagenesis screen to detect and establish mutant mouse lines with a high aldosterone phenotype