The effects of ovarian hormones upon the female genital tract have been extensively studied (see Parkes & Deanesly, 1966a), but very little is known of the effect of ovarian steroids on the early development of the mammalian embryo. It has been shown that oestrogens and progesterone enhance the incorporation of labelled uridine and labelled amino acids in delayed blastocysts of certain mammals (Prasad, Dass & Mohla, 1968; Weitlauf & Greenwald, 1968). On the other hand, studies in vitro have shown that progesterone has an inhibitory effect on the early development of mammalian embryos as judged by the arrest of cleavage (Whitten, 1957; Daniel, 1964; Kirkpatrick, 1971). In the presence of macromolecules of the uterine fluid, however, progesterone in vitro has a stimulatory effect as measured by the growth of rabbit blastocysts (El-Banna & Daniel,
L. Roblero and L. Izquierdo
Laboratory of Embryology, Institute of Biological Sciences, Catholic University of Chile and Faculty of Sciences, University of Chile, Santiago, Chile
L. S. Roblero and Anita C. Garavagno
Summary. Transport of embryos through the oviduct, cleavage rate and transformation of morulae to blastocysts, were delayed in females ovariectomized on Day 2 of pregnancy. Oestradiol-17β in doses of 60 to 6000 pg/day for 3 days did not normalize the transport of embryos, but the transformation of morulae to blastocysts reached values near or equal to those of the controls, in spite of a lowered rate of cleavage. Progesterone at a dose of 100 μg/day, resulted in normal transport, rate of cleavage and rate of differentiation. Treatment with both hormones had synergistic effects on transport and the rate of cleavage and differentiation. These results give further support to the concept that ovarian hormones are the controlling factors for these processes in early pregnancy.
L. Roblero, J. D. Biggers and C. P. Lechene
Department of Physiology and Laboratory of Human Reproduction and Reproductive Biology, Harvard Medical School, 45 Shattuck Street, Boston, Massachusetts 02115, U.S.A.