The corpora lutea of several species contain estrogen receptors, but the role of estrogens in luteal function is unclear in most species. In this study, we investigated the direct effect of estradiol-17 beta (E2) and catecholestrogens (2-OHE2 or 4-OHE2) on rat and pig luteal steroidogenesis using in vitro cultures of small (SLC) and large (LLC) luteal cells prepared by elutriation. SLC and LLC were cultured at 37 degrees C for 36 h in serum-free media and treated with E2, 2-OHE2, or 4-OHE2; LH; forskolin (FORS); dibutyryl cAMP (dbcAMP); or combinations thereof. In the rat, E2 (2.5-10 micrograms/ml) inhibited progesterone (P4) production by both cell types dose-dependently. P4 production by rat SLC increased with increasing dose of 4-OHE2 up to the 2.5-microgram dose, then decreased to near control level at the 10-microgram dose. In LLC, P4 production in the presence of 4-OHE2 decreased initially (up to 2.5 micrograms/ml 4-OHE2), then increased at the 10-microgram dose. LH, FORS, and dbcAMP stimulated P4 production by SLC and LLC. For SLC, the stimulatory effects of LH and 4-OHE2 (2.5 micrograms) were comparable but lower than those of FORS and dbcAMP. For LLC, the effects of 4-OHE2 (10 micrograms), LH, and FORS were comparable but lower than those of dbcAMP. In time-course experiments, E2 inhibition of P4 production was observed at 36 and 72 h but not 6 h of culture for SLC and at all time points for LLC.(ABSTRACT TRUNCATED AT 250 WORDS)