Estradiol receptor levels in spontaneous leydig cell tumors of fischer rats

Abstract

Spontaneous Leydig cell tumors were found in a high proportion of Fischer rats after the age of 1 year. At 2 years of age, virtually all the testes were affected to various degrees. Cytosolic estradiol receptors with properties identical to those of normal testes were increased 2- to 10-fold in Leydig cell tumors. Nuclear receptors were found to be lower in normal Fischer rat testes than in Sprague-Dawley rats [75 ± 12 (SD) fmol/mg DNA vs 104 ± 3 (SD) fmol/mg DNA]. However, 1 h after a single injection of 25 μg of estradiol, the nuclear receptor levels were increased 1.4-fold in Sprague-Dawley rats and 2.9-fold in normal Fischer rats. The unstimulated nuclear receptor levels in testicular tumors were higher than in normal Fischer rat testes and similar to Sprague-Dawley rat testes. After estradiol injection, normal testes and testicular tumors from Fischer rats had similar estradiol receptor levels [218 ± 49 (SD) and 211 ± 106 (SD) fmol/mg DNA]. These subtle changes in nuclear estrogen receptor concentrations do not support nor disprove the hypothesis that estrogens are implicated in the development of testicular tumors in Fischer rats.