Objectives:The SA-gene shows markedly higher levels of expression in the kidneys of spontaneously hypertensive rats (SHR) than in their non-hypertensive reference strain, the Wistar-Kyoto (WKY) rat. Based on the important role of the kidney in blood pressure regulation, the possibility has been raised that this gene, the translational product of which remains unknown, may participate in the pathogenesis of primary hypertension. The present study was conducted to test this hypothesis and to ascertain the chromosomal localization of the SA-gene.Design:A cosegregation study was performed using an F2intercross between strokeprone SHR (SHRSP) and WKY rats, and a previously described restriction fragment length polymorphism of the SA-gene for characterization of genotype. Mapping of the SA-gene was accomplished by screening a somatic cell-hybrid panel and by linkage group analysis.Results:A statistically significant difference in systolic blood pressure was found after sodium loading, but not under basal conditions between groups of rats defined by zygosity at the SAlocus, consistent with a hypertensive effect of the SHRSP allele. No effect of SAgenotype on diastolic blood pressure was observed. The SA-gene was localized on rat chromosome 1.Conclusions:This study establishes the SAlocus on chromosome 1 as a region in which a gene or genes contributing to blood pressure regulation in this model are localized, and provides further evidence for a possible role of the SA-gene in the pathogenesis of hypertension.