FAILURE OF THE HEAT-SHOCK PROTEIN-70 LOCUS TO COSEGREGATE WITH BLOOD-PRESSURE IN SPONTANEOUSLY HYPERTENSIVE RAT X WISTAR-KYOTO RAT CROSS

Objective: To investigate the involvement of the heat-shock protein 70 (hsp70) locus, located in the rat major histocompatibility complex (RT1), in hypertension of the spontaneously hypertensive rat (SHR). Previous studies have shown abnormal expression of hsp70 in the SHR and an association of the SHR hsp70 allele with increased blood pressure in recombinant inbred strains derived from a cross of SHR with Brown-Norway rats. Design: SHR were crossed with normotensive Wistar-Kyoto (WKY) rats to produce a large cohort of F2 rats segregating for blood pressure and hsp70 alleles. Two hundred and thirty-three rats were maintained on a normal-salt diet and 167 were put on a high-salt diet (1% sodium chloride in drinking water) from 16 to 26 weeks of age. Methods: Blood pressure was measured indirectly at 12, 16 and 20 weeks of age in rats on the normal-salt diet and at 16 (pre-salt), 18 and 20 weeks in rats on the high-salt diet. Both groups had direct conscious blood pressure measurements at 25-26 weeks of age. Genotyping was carried out for a BamH1 polymorphism in the hsp70 gene by Southern blotting. Results: The hsp70 genotype had no effect on any of the blood pressure measurements in rats on either diet. Conclusions: We find no evidence of linkage between the hsp70 gene locus, and by implication other genes located within the rat RT1 complex, and blood pressure in our cross of SHR and WKY rats.