The detection of oestrogenic activity by measurements of nucleic acid concentrations in serial samples of ovine uterine tissue obtained by biopsy

Abstract

The potential occurrence of phyto-oestrogenic activity in tropical pasture species, which are grazed almost exclusively by cattle in Australia, was assessed by a new technique based on changes in the ratio of concentrations of nucleic acids in ovine uterine tissue. Cast-for-age ewes ovariectomized on the 12th day after oestrus were subjected 14 days later to oestrogenic stimulation; samples of uterine tissue were obtained by biopsy before and after the administration of oestrogen. Significant increases in the ratio of nucleic acid concentrations, RNA/DNA, were obtained in response to the administration of 5, 10 and 20 µg stilboestrol dipropionate intramuscularly daily for 3 and 5 days. The variance of the response was mainly affected by the dose of stilboestrol, and a significant effect due to the duration of treatment was detected. It was concluded that the technique will detect levels of phyto-oestrogenic activity substantially below those likely adversely to affect reproduction in cattle.