Abstract
Genetic factors controlling the deoxyribonuclease I (DNase I) activity level were examined in mice. A survey of inbred strains of mice revealed genetic variation in urinary and kidney DNase I activity levels, though a sex difference, males having significantly higher DNase I activity levels than females, was observed in all mouse strains tested. The sex difference in the urinary DNase I activity level was eliminated by testosterone administration to females or gonadectomy to males. The urinary DNase I level was closely correlated to that of the kidneys but no relationship between serum and urinary DNase I activity suggests that the production ratio of DNase I in the kidneys is responsible for strain variation in urinary DNase I levels. Inheritance of quantitative variation of urinary DNase I activity levels was studied by a test cross. The segregation ratio of backcross progenies fitted the model showing that urinary DNase I activity level was controlled by an autosomal single locus, Dna1 (χ2=0.1053, P>0.90). The allele Dna1ra determines high DNase I inducibility in the kidneys and occurs in BALB/c, C3H/He and A/J strains. The allele Dna1rb determines low DNase I inducibility in the kidneys and occurs in DBA/2 and C57BL/6 strains.
