Equol is known to be a selective androgen modulator and has the ability to bind and inhibit 5-alpha dihydrotestosterone (5α-DHT). Equol is also a selective estrogen receptor modulator and is able to bind beta estrogen receptors with high affinity. As estrogen receptors are found in the hypothalamus, pituitary, and gonads, prenatally administered equol could affect the morphological and reproductive development of offspring. To test this hypothesis, during gestational days 14 to 20, forty-two pregnant Long-Evans rats were given one of six treatments: 1) no treatment, 2) injection with dimethyl sulfoxide (DMSO), 3) injection with 10 mg/kg equol, 4) injection with 21.0 mg/kg equol, 5) injection with 63.0 mg/kg equol, or 6) injection with 90.0 mg/kg flutamide. At birth the pups were weighed, anogenital distance measured, and sex was determined. Some of the animals were sacrificed and trunk blood collected from both the mothers and pups. Serum levels of phytoestrogens, estradiol, testosterone, and 5α-DHT levels were determined. Some pups were allowed to grow up to day 29 and were tested on the forced-swim test with the parameters of time mobile, time immobile, swim distance, and average speed measured. The flutamide treated pups had the lowest anogenital distance. The low equol dose animals had the largest anogenital distance. There were no significant differences in 5α-DHT serum levels in the male offspring among the treatments. However in non-injected control female offspring displayed significantly lower 5α-DHT levels than all the other groups. Mothers treated prenatally with equol displayed significantly higher circulating equol levels compared to controls values. Rats injected with 63.0 mg/kg of equol gained the least weight during pregnancy. Their offspring also had the lowest body weights at birth. Male and female offspring displayed similar behaviors in the Porsolt forced-swim test among the treatment groups. The low and high equol groups displayed the least depressive-like behaviors. The offspring from mothers treated with the medium and high equol doses both gained the most weight from birth to day 29. Treating pregnant rats with equol during the last week of gestation does not appear to have any affect on morphological genital development of the offspring.



College and Department

Life Sciences; Physiology and Developmental Biology



Date Submitted


Document Type





equol, phytoestrogens, behavior, morphological development, rat