ANALYSIS OF QUANTITATIVE TRAIT LOCI FOR BLOOD-PRESSURE ON RAT CHROMOSOME-2 AND CHROMOSOME-13 - AGE-RELATED DIFFERENCES IN EFFECT

Previous studies have suggested the presence of quantitative trait loc i (QTLs) influencing blood pressure on rat chromosomes 2 and 13. In th is study, rye mapped the QTLs in F-2 rats derived from a cross of the spontaneously hypertensive rat and the Wistar-KS oto rat and analyzed the effect of the QTLs on blood pressures measured longitudinally betw een 12 and 25 weeks of age. We analyzed 16 polymorphic markers spannin g 147.3 cM on chromosome 2 and 13 markers spanning 91.6 cM on chromoso me 13. Both chromosomes contained QTLs with highly significant effects on blood pressure (peak logarithm of the odds [LOD] scores, 5.64 and 5.75, respectively). On chromosome 2, the peak was localized to a posi tion at anonymous marker D2Wox7, 2.9 cM away from the gene for the sod ium-potassium ATPase alpha(1)-subunit. On chromosome 13, the major pea k coincided with the marker D13Mit2, 21.7 cM away from the renin gene, but there was a suggestion of multiple peaks. The effect of the QTL o n chromosome 2 was seen throughout from 12 to 25 weeks of age, whereas interestingly, the effect for the QTL on chromosome 13 was maximal at 20 weeks of age but disappeared at 25 weeks of age. presumably becaus e of the effect of either epistatic factors or environmental influence s. The findings provide important information on QTLs influencing bloo d pressure on rat chromosomes 2 and 13 that will be useful in localizi ng and identifying the causative genes and emphasize the importance of age bring taken into account when the effects of individual QTLs on a trait that shows significant age-related changes are being analyzed.