Serum and tissue levels of estradiol during estrogen-induced renal tumorigenesis in the Syrian hamster

Abstract

The estrogen-induced renal tumor in the hamster has emerged as a major animal model in hormonal carcinogenesis. However, a fundamental aspect of this experimental model has as yet not been investigated. In the present study, comparisons between the serum and tissue 17β-estradiol (E 2) levels in cyclic female hamsters and corresponding hormone levels in E 2-treated castrated male hamsters have been made. Data is provided concerning the concentration of estrogenic hormones in the serum and target tissue typically required to elicit renal tumorigenesis in this species. Serum E 2 levels in the cyclic female hamster average 79 pg/ml on days 1–2 and 311 pg/ml on days 3–4, attaining a maximum of 358 [g/ml on day 4 of the cycle. Elevation in uterine, renal and hepatic E 2 tissue levels during days 3–4 of the cycle reflect increases in serum E 2 levels which were 3.0-, 2.0-, and 2.6-fold higher when compared to day 1 of the cycle in these tissues. As expected, serum E 2 levels of untreated castrated male hamsters did not appreciably vary over a 6 month period of aging and averaged about 32 pg/ml. Under conditions which produced essentially 100% renal tumor incidence, a rapid rise in serum E 2 levels, averaging 71.0-fold higher than untreated castrated levels, was seen. A steady state serum E 2 level of 2400 to 2700 pg/ml was maintained from 45–180 days of continuous estrogen treatment. Compared to kidneys of untreated hamsters, renal E 2 levels in E 2-treated hamsters rose only on average 5.4-fold between 15–180 days of hormone exposure. Serum levels of E 2-treated hamsters were 5.7- to 8.0-fold higher than those observed in cyclic female hamsters on days 3 and 4. However, at these higher E 2-treated serum levels there was no apparent effect either on weight loss or mortality of the animals.