THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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1974; Fellows et a1, 1974¡ Handwerger et a:-, L974¡ Martal
et al, 1975; Bolander et aI, L976i Chan et al, J.976). In
our Laboratory, r¡¡e have Ídentified and quantitated placenta]
lactogen concentrations in the circulation of human, nonkey,
rat, mice, haÍìster, guinea pig, cow, goat and sheep using
these assays (KeIIy, 197 6).
Order Lagomorpha (Rabbits) :
pregnancy is terminated at any st,age by hypo_
physectomy or by ovariectomy in the rabbit. The pituitary
complex required to maintain Luteal function hàs been
studied in femaLes hypophysectomized on day ? and g of
pregnancy and treated Ìrrith hormones for a furùher 7 or g
days f. Spies et aJ., 1968). FsH, prolactin and possibly
also LH are required, ar-though these hormones at the doses
used did not support normal fetuses. Thus, it appears that
t.he placenta alone cannot províde an adequate luteotropic
stimulus during pregnancy.
There is very littte quantitat,ive infor¡nation
available on ma¡nmary gland development in rabbits hypophy_
sectomized during pregnancy. In hypophysectomi zed pregnant,
femal-es maintained on either progesterone (Robson, L936) or
estrogen (Robson, 1937, 1939), the mammary gland is not so
well devel-oped as in normal pregnancy, but, Ít apparently
does not compleÈely regress. This may indicate some placental
mammotropin (placentaì. lactogen) secretion, but since
estrogen and progesterone can produced limited rnammary gland