Renal Expression of Dahl SS/Jr (S) and Congenic Rats after 24 hours of Dietary Salt Loading

The overlap of congenic regions in an earlier substitution mapping study suggested the location of two blood pressure quantitative trait loci (QTL)-containing regions in the q-terminus of rat chromosome 3, QTL1 and the more distal, QTL2. Male SS/jr rats and two congenic substrain rats S.R(D3Mco36-D3Mco46) and S.R(D3Mco36-D3Got166) were maintained on a low salt (0.4% NaCl Harlan Teklad diet TD7034) diet until 39-41 days of age. These 3 rat strains will be hereafter referred to as S, S.R(ET3x1), and S.R(ET3x2), respectively. At 39-41 days of age, half of the rats from each strain were fed a high (4% NaCl Harlan Teklad diet TD83033) salt diet and water ad libitum for 24 hours. Both congenic substrains carry SR/jr (R)-rat alleles for QTL2 on an S-rat genetic background, while S.R(ET3x2) also carries R-rat alleles for QTL1. Renal gene expression analysis was used to identify differentially expressed genes or genes with altered activity within the S.R(ET3x2) congenic region. Keywords: strain differences in response to dietary changes Age-matched male S (n=10), S.R(ET3x1) (n=8), and S.R(ET3x2) (n=8) rats were bred, housed, and studied concomitantly to minimize envi¬ronmental effects. Rats were weaned at 30 days of age onto a low salt diet (0.4% NaCl, Harlan Teklad diet TD7034) and water ad libitum. At 39-41 days of age one-half of rats from each strain group were switched to a 4% NaCl diet (Harlan Teklad diet TD83033) and water ad libitum for 24 hours. Rats were then killed with pentobarbitol overdose. Gene expression data from Affymetrix Rat RAE230 A and B GeneChips, hybridized with kidney cRNA, was used to identify genes with altered activity within the S.R(ET3x2) congenic region.