Schwann cells dissociated from sciatic nerves of 4- to 5-day-old rats were established in long-term primary cultures. After treatment with anti-Thy-1.1 and complement, pure Schwann cell cultures were obtained as confirmed by indirect immunofluorescence staining of the S-100 antigen. The effect of estradiol on Schwann cell proliferation was tested. The estrogen alone had no effect on cell multiplication, but in the presence of forskolin (5 microM) or dibutyryl cyclic AMP (dbcAMP, 1 microM), estradiol (100 nM) became a potent mitogen. This effect was specific since when the anti-estrogen ICI-164,384 (200 nM) was added to the cultures, it completely inhibited the mitogenic effect of estradiol. In the absence of the estrogen, ICI-164,384 did not inhibit dbcAMP-induced cell growth. The effect of progesterone was also tested in the presence of forskolin, and no influence on cell multiplication was seen. Specific and saturable binding sites for estradiol were measured in Schwann cells by whole cell assay after labeling cells at 37 degrees C with [3H]estradiol and about 3000 specific binding sites per cell were found. Treatment of the cultures with forskolin (5 microM) for 48 or 72 h, but not for shorter times, resulted in a two-fold increase in estradiol binding. Estrogen receptors were visualized inside Schwann cells with a monoclonal anti-ER antibody by indirect immunofluorescence staining. Double-label immunofluorescence of ER and S-100 showed that ER immunostaining was restricted to spindle-shaped Schwann cells expressing the S-100 antigen.(ABSTRACT TRUNCATED AT 250 WORDS)