Two blood pressure/cardiac mass quantitative trait loci on Chromosome 3 in Dahl rats

. Interval mapping was used to identify putative quantitative trait loci (QTL) for blood pressure and cardiac mass on Chromosome (Chr) 3 in F 1 (S × R) × S population of 150 rats raised on an 8% NaCl diet. Two genetic markers 95.7 cM apart, D3Wox3 and D3Mco5 (tightly linked to Edn3 ), showed ``suggestive'' linkage to blood pressure (LOD = 2.0 and 1.8 respectively). In addition, D3Wox3 showed ``suggestive'' linkage to heart weight (LOD = 2.5), and D3Mco5 showed ``suggestive'' linkage to body weight–adjusted heart weight (LOD = 2.1). Congenic rats (designated S.R-Edn3) were constructed by introgressing the R-rat Edn3 allele (and flanking loci) into the S strain. On a 2% NaCl diet, S.R-Edn3 rats had lower blood pressure (21.4 mm Hg, P = 0.0005) and heart weight (59 mg, P = 0.0038) compared with S rats, confirming the existence of a blood pressure QTL on Chr 3 near Edn3 even though QTL linkage analysis of blood pressure did not achieve stringent statistical criteria for significance. The results of the congenic experiment and the large distance between the two putative QTL suggest the presence of at least two independent blood pressure/cardiac mass QTL detectable on Chr 3 in the Dahl rat model of genetic hypertension.