Localization of a blood pressure QTL on rat chromosome 1 using Dahl rat congenic strains

We previously reported that markers on rat chromosome 1 are genetically lin ked to blood pressure in an F-2 population derived from Dahl salt hypertens ion-sensitive (S) and Lewis (LEW) rats. Because there was evidence for more than one blood pressure quantitative trait locus (QTL) on chromosome 1, an initial congenic strain introgressing a large 118-centimorgan (cM) segment of LEW chromosome 1 into the S background had been constructed. This initi al congenic strain had a reduced blood pressure compared with S rats, provi ng the existence of a blood pressure QTL, but not giving a good localizatio n of the QTL. In the present work a series of five overlapping congenic sub strains were produced from the original congenic strain in order to localiz e a blood pressure QTL to a 25-cM region near the center of chromosome 1. T he congenic substrains also ruled out the Sa locus as a blood pressure QTL in the S vs. LEW comparison because the Sa locus was contained in a congeni c substrain that did not alter blood pressure.