Concentrations of oestradiol-17 in plasma and corpora lutea throughout pregnancy in the tammar, Macropus eugenii

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Abstract
Summary. Oestradiol-17β concentrations were measured by radioimmunoassay in peripheral blood samples from 10 tammar wallabies after their pouch young were removed to terminate embryonic diapause. Oestradiol concentrations rose from 8·3 ± 1·2 pg/ml on Days 3 and 4 to a peak of 15·8 ± 2·9 pg/ml on Day 5, coincident with an increase in 'progesterone' concentrations, and then fell to 10·5 ± 2·7 pg/ml on Day 7. No changes in oestradiol concentrations were associated with parturition. Five females came into oestrus and mated 9·8 ± 6·1 h post partum; peak concentrations of plasma oestradiol (20·9 ± 2·1 pg/ml) occurred around the time of mating. None of the females that did not mate up to the end of the experiment at Day 30 had a rise in plasma oestradiol concentrations. Corpora lutea contained 20-100 pg oestradiol during pregnancy. The highest ovarian oestradiol content (> 1200 pg) was measured in whole ovaries containing Graafian follicles from full-term pregnant females. The rise in oestradiol concentrations at Day 5 may be important in the termination of diapause. The post-partum increase in plasma oestradiol concentrations coincides with oestrus. The source of this oestrogen appears to be the preovulatory follicle.

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