BLOOD-PRESSURE IN GENETICALLY HYPERTENSIVE RATS - INFLUENCE OF THE Y-CHROMOSOME

We used a cross between the stroke-prone spontaneously hypertensive ra t (SHRSP) strain and the Wistar-Kyoto (WKY) normotensive strain to elu cidate the genetic basis of hypertension. Previous studies have report ed conflicting evidence for the contribution of the Y chromosome to hy pertension in these models. To investigate further the role of the Y c hromosome in hypertension, we performed two large reciprocal crosses: one with the SHRSP as a male progenitor of the cross, yielding 60 F-2 rats, and another with the WKY as a male progenitor, yielding 83 F-2 r ats. The resulting F-2 hybrids were phenotyped with the use of a radio telemetry system (Data Sciences) for measurement of systolic, diastoli c, and mean arterial pressures as well as heart rate and motor activit y continuously for 96 hours at baseline and after 1% NaCl was added to the rats' drinking water for 12 days. Male F-2 hybrids with the SHRSP grandfather had significantly higher average systolic, diastolic, and mean arterial pressures at baseline compared with male F-2 hybrids wi th the WKY grandfather (188.7 +/- 18.1 versus 168.9 +/- 11.5, 130.3 +/ - 14 versus 115.7 +/- 7.3, and 159.1 +/- 15.8 versus 141.5 +/- 9.4 mm Hg, respectively). These differences were also observed after salt loa ding (197.9 +/- 22.1 versus 176.5 +/- 11.7, 136.5 +/- 17.3 versus 120. 7 +/- 7.6, and 166.7 +/- 19.5 versus 148 +/- 9.7 mm Hg, respectively; P<.0001 for each comparison). These results suggest that the SHRSP Y c hromosome contains a locus or loci that contribute to hypertension in SHRSP/WKY F-2 hybrids.