GENETIC CONTAMINATION OF DAHL SS JR RATS - IMPACT ON STUDIES OF SALT-SENSITIVE HYPERTENSION/

The Dahl salt-sensitive rat (SS/Jr) is a widely used animal model of s alt-sensitive hypertension. SS/Jr rats are believed to be highly inbre d and uniformly sensitive to the hypertensinogenic effects of sodium c hloride, but we have recently observed that SS/Jr rats from Harlan Spr ague Dawley, Inc, exhibit considerable variability in their blood pres sure response to supplemental dietary salt. To test the possibility th at commercially available SS/Jr rats are genetically contaminated and therefore no longer fully inbred, we performed molecular genetic studi es and blood pressure measurements in several groups of SS/Jr rats pur chased from Harlan Sprague Dawley. We found molecular evidence of hete rozygosity and/or atypical allelic variants involving loci on at least five different chromosomes. Many of the rats also failed to exhibit a salt-sensitive blood pressure phenotype. We conclude that SS/Jr rats being sold by the only commercial vendor of Dahl rats in the United St ates are genetically contaminated and resistant to the hypertensinogen ic effects of salt. These findings raise serious questions about the i nterpretation of research conducted with SS/Jr rats obtained from Harl an Sprague Dawley.