4,4'-Diaminodiphenylmethane (4,4'-methylenedianiline) (
DDPM) promoted the development of thyroid
tumors in rats treated with a subeffective dose of
N-bis(2-hydroxypropyl)nitrosamine (2,2'-dihydroxy-N-nitrosodipropylamine) (
DHPN) for thyroid
tumorigenesis. Male inbred W rats were given a single ip injection of 280 mg
DHPN/100 g
body weight and fed diets with or without 1,000 ppm
DDPM. Thyroid
tumor incidences at the end of week 20 of the experiment were 90% (19/21) in rats given
DHPN and then
DDPM and 28% (6/21) in rats given
DHPN alone. The incidence of
thyroid cancers was 9.5% (2/21) in rats first given
DHPN and then
DDPM. Untreated rats and rats given
DDPM alone had no thyroid
tumors after 20 weeks. Incidences of kidney
tumors were 38% (8/21) in rats given
DHPN and then
DDPM and 28% (6/21) in rats given
DHPN alone. No
tumors were found in the kidneys and lungs of rats given
DDPM alone and in those of control rats. Treatment with
DDPM alone slightly but not significantly decreased the serum concentrations of
thyroxine and
triiodothyronine; treatment with
DHPN plus
DDPM had no such effect.