Abstract
A blood pressure (BP) quantitative trait locus (QTL) was previously located within 117 kb on rat chromosome 9 (RNO9) using hypertensive Dahl salt-sensitive and normotensive Dahl salt-resistant rats. An independent study between two hypertensive rat strains, the Dahl salt-sensitive rat and the spontaneously hypertensive rat (SHR), also detected a QTL encompassing this 117 kb region. Dahl salt-sensitive alleles in both of these studies were associated with increased BP. To map SHR alleles that decrease BP in the Dahl salt-sensitive rat, a panel of eight congenic strains introgressing SHR alleles onto the Dahl salt-sensitive genetic background were constructed and characterized. S. SHR(9)x3B, S. SHR(9)x3A and S.SHR(9)x2B, the congenic regions of which span a portion or all of the 1 logarithm of odds (LOD) interval identified by linkage analysis, did not significantly alter BP. However, S.SHR(9), S.SHR(9)x4A, S. SHR(9)x7A, S. SHR(9)x8A and S. SHR(9)x10A, the introgressed segments of which extend distal to the 1 LOD interval, significantly reduced BP. The shortest genomic segment, BP QTL1, to which this BP-lowering effect can be traced is the differential segment of S. SHR(9)x4A and S. SHR(9)x2B, to which an urinary protein excretion QTL also maps. However, the introgressed segment of S. SHR(9)x10A, located outside of this QTL1 region,