Role of embryonic oestrogen in rabbit blastocyst development and metabolism

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Abstract
Rabbit morulae were grown for 24 h in Ham''s F12 medium supplemented with BSA [bovine serum albumin]. CI-628 citrate (1.5 .mu.g/ml), a specific estrogen antagonist, significantly inhibited the transformation of morulae to blastocysts. This inhibition was reversed with estradiol-17.beta. (1 .mu.g/ml) but not estradiol-17.alpha. (1 .mu.g/ml) added to the culture medium. The specific activities of phosphofructokinase, lactic dehydrogenase, malate dehydrogenase and alkaline phosphatase in blastocysts grown in vitro for 24 h in medium TC 199 + BSA showed significant elevation with blastocyst growth and expansion, while that of acid phosphatase revealed no change, and leucine aminopeptidase activity declined significantly. These changes were markedly inhibited by CI-628 citrate (2 .mu.g/ml) and were reversed by estradiol-17.beta. (0.4 .mu.g/ml) but not by estradiol-17.alpha. (0.4 .mu.g/ml). A role of estrogen present in the rabbit morula and blastocyst in the triggering of embryonic differentiation and metabolic functions is suggested.