ESTIMATE OF THE GENETIC-DIVERGENCE BETWEEN INBRED DAHL SALT-SENSITIVEAND SALT-RESISTANT RATS

Objective: The genetic divergence of inbred Dahl salt-sensitive (SS/Jr ) rats from inbred Dahl salt-resistant (SR/Jr) rats and various other inbred strains was measured. Design: Structural differences in DNA bet ween strains were evaluated. Methods: Genetic variants were sought (1) by restriction fragment length polymorphism (RFLP) analysis, using 19 DNA probes, (2) by the polymerase chain reaction around microsatellit es and (3) by DNA sequencing. Results: It was estimated that 1 in 1532 bases of DNA were different between the SS/Jr and SR/Jr strains. In c omparing SS/Jr and SR/Jr rats, it was also observed that one DNA probe in 10 will yield multiple RFLP, presumably as the result of large ins ertion/deletion events. A comparison of SS/Jr rats with seven other in bred strains showed that the percentage of loci that carry alleles dif ferent from SS/Jr rats varies from about 23% for Albino Surgery rats t o 71% for Brown Norway rats. Conclusions: Although the SR/Jr strain is an appropriate contrasting strain for the genetic analysis of hyperte nsion in SS/Jr rats, a genetic analysis involving crosses of SS/Jr rat s and unrelated inbred strains is also likely to be useful in identify ing genes that cosegregate with blood pressure because more informativ e genetic markers will be available than in a cross of SS/Jr with SR/J r rats.