Genetic control of blood pressure in mice.

HE role of genetics in determining arterial blood pressure has been the s u b of numerous papers in the medical literature. Familial aggregation of blood pressure levels is well documented in human populations (summarized by MCKUSICK 1960; SCHTNEITZER et al. 1962; ROBERTS 1964). Although there is little doubt that genetic factors to some degree determine systolic blood pressure levels. there is some question as to the number of genes involved. The evidence for a single dominant gene (PLATT 1963) and for multifactorial determination (HAMILTON and PICKERING 1963) of essential hypertension was described in detail by ROBERTS. MIALL and OLDHAM (1963) suggested that 33 to 45% of the variation in systolic blood pressures in human populations could be explained by genetic factors. Genetic influences were also indicated in experimental animal colonies where selectioii resulted in lines of hypertensive rabbits (ALEXANDER, HINSHAW and DRURY 1954) and rats (SMIRK and HALL 1958; OKAMOTO and AOKI 1963), and of rats sensitive or resistant to the hypertensive effects of salt ingestion (DAHL, HEINE and TASSINARI 1965). Heritability estimates are available for chickens (280/,, STURKIE et al. 1959) and mice (20 to 45%, SCHLAGER 1965). This paper will deal with the results of three separate investigations into the mode of inheritance of blood pressure in mice and the relative importance of genetic and environmental factors in determining this trait. The three studies were a survey of 19 inbred strains, a diallel cross of four strains, and an examination of the F, and backci-osses from a cross of a high and low blood pressure strain. Evidence will be presented demonstrating that systolic blood pressure in populations of mice has a continuous distribution determined in part by more than one pair of alleles acting additively with some dominance in specific crosses.