QUANTITATIVE TRAIT LOCI IN GENETICALLY HYPERTENSIVE RATS - POSSIBLE SEX SPECIFICITY

We performed a total genome screen in an Fz cross derived from the str oke-prone spontaneously hypertensive rat and the normotensive Wistar-K yoto rat. Blood pressure at baseline and after 1% NaCl was measured by radiotelemetry; other phenotypes included heart rate, motor activity, left ventricle weight to body weight ratio, and vascular smooth muscl e cell polyploidy, a measure of vascular hypertrophy. Quantitative tra it loci affecting a given phenotype were mapped relative to microsatel lite markers by using the MAPMAKER/QTL 1.1 computer package. We identi fied three blood pressure quantitative trait loci, two on rat chromoso me 2 and one on rat chromosome 3. The quantitative trait loci close to genetic markers D2Mgh12 (''suggestive'' linkage, with a maximal logar ithm of the odds [LOD] score of 3.1) and D3Mgh16 (significant linkage, with a maximal LOD score of 5.6) showed possible sex specificity in t he male F-2 cohort only. This was confirmed by the likelihood ratio te st for the difference in locus effects between the sexes. We also iden tified a new quantitative trait locus for LV hypertrophy on rat chromo some 14 (''suggestive'' linkage, with a maximal LOD score of 3.1). The sex specificity of blood pressure quantitative trait loci will be imp ortant in designing congenic strains and substrains for fine genetic m apping and for identifying genes that regulate blood pressure.