PROGESTERONE RECEPTORS IN ESTROGEN-INDUCED FIBROMATOSIS OF GUINEA-PIGS

The presence of estrogen and progesterone receptors was investigated in estrogen-induced guinea pig fibromatosis. These lesions were composed of fibroblast-like cells embedded in abundant collagen which stained positively for desmin and vimentin suggesting muscler and fibroblast differentiation. Cytosolic progesterone receptors ranging from 13 to 2045 fmol/mg protein were present in 10 13 samples while nuclear progesterone receptors were detected in 7 10 samples with values ranging from 8 to 4639 fmol/mg DNA. The Kd of the cytosolic progesterone receptor measured by a Scatchard analysis yielded a value of 3.35 × 10-9 M with a sedimentation coefficient of 9S as determined by a sucrose gradient. Estrogen nuclear binders were found in 9 10 samples ranging from 6 to 282 fmoles/mg DNA and cytosolic estrogen binders in 10 13 with values of 9 to 349 fmoles/mg protein. The Kd of the cytosolic estrogen binder was 22 × 10-9 M. This binder was not detected by a commercially available monoclonal antibody. Estrogen cytosolic binders and progesterone cytosolic receptors were also detected in some samples of non tumoral fibrotic tissue. It is concluded that this experimental model is appropriate for the investigation of the effects of estrogen and progesterone on proliferative fibroblastic lesions. © 1990.