The objective of our study was to determine the genetic influence on blood pressure in spontaneously hypertensive rats (SHR), and normotensive Wistar-Kyoto (WKY) rats using genetic crosses. Blood pressure was measured by tail sphygmomanometry from 8 to 20 weeks of age. Blood pressure was significantly higher from 12 to 20 weeks in the male offspring derived from WKY mothers x SHR fathers as compared with male offspring derived from SHR mothersxWKY fathers (180±4 versus 160±5 mm Hg, /?\u3c0.01). There was no significant difference between the blood pressure of the F, females, further supporting Y chromosome linkage and not parental imprinting. The blood pressure data from F2 males derived from reciprocal crosses of parental strains were consistent with the presence of a Y-Iinked locus, but not with an X-linked locus controlling blood pressure. The data strongly suggest that hypertension in the SHR has two primary components of equal magnitude, one consisting of a small number of autosomal loci with a second Y-linked component
