ASSOCIATION OF SALT SENSITIVITY IN RATS WITH GENES OF THE MAJOR HISTOCOMPATIBILITY COMPLEX

Dietary sodium intake has long been considered an important factor in the genesis and maintenance of hypertension in both humans and experim ental animals. To identify the possible association between salt sensi tivity and genes of the major histocompatibility complex (RT1 complex) , we studied the blood pressure response to an 8% NaCl diet in normote nsive Lewis rats, spontaneously hypertensive rats (SHR), and Lewis.1K congenic rats (congenic to Lewis with the SHR main histocompatibility complex RT1). During the first 4 weeks of a high salt diet, the blood pressure increase was the same in SHR and Lewis.1K congenic rats. Thus , the presence of a small segment of SHR chromosome 20 with genes of t he RT1 complex (and closely related genes) in the Lewis genome sensiti zed the blood pressure of these animals to the hypertensive effects of a high salt diet. Genes of the RT1 complex influenced the salt-induce d increase of relative kidney weight more than that of relative heart weight. Our results support the hypothesis that some alleles within or close to the RT1 complex might be responsible for the higher sensitiv ity of hypertensive individuals to certain environmental stressors, in cluding high salt intake.