THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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Pregnarit Marê Sêrum Gonâdót¡opln (pMSc)
Before the concept of a ',placental gonadotropin,' was we.ll
established, Co'le and Hart (1930) annouced thelr finding of gonadotropic
activity in the serum of the pregnant mare. Zondek(.1934) detected th.is
activity almost simultaneousìy. As in the case of hCG, an extensive
literature rapidly developed around thjs factor which soon became
known as pregnant mare serum gonadotropin (pMsG), Later studies showed that
PMSG is simllar to hCG but with a somewhat different ratio of LH
to FSH-activity. An origin in materna'l fissue was claimed for pMSG
by Cìegg et a] (1934) and by Gonz a'l ez-Angu I o et aì
(1972'). A recent report by Aì]en et al (1972) presented evidence for
chorlonic origin whìch consisted of in vitro production of the
hormone by chorionic girdle cells.
The molecular weight of pMSG remains uncertain. Bourrillon
and Got(]959) obtained a morecurar welght of 28,000 for pMSG empìoying
sedinentation analysis. However, size determinafion by means of polyacry_
lamide geì electrophoresìs containing sodium dodecyl sulfate (SDS)
suggests PMSG may have a moìecular weight as high as 53,000 (Gospodarowicz,
1972). Papkoff(1974) recently reported the dissociation of pMSG into
alpha and beta subunits which possessed very low biological activity.
Recombination of these subunits restored both the FSH-'I ike and LH-tike
b'iological properties. Bourrillon and Got (.l9s7) emproyed zone electro-
phoresis to obtain an isoerectric point of l.B for pMsG. The carbohydrate
content of PMSG is higher than that of the other gonadotropins, comprising
nearly 50% of the weight of the moìecule. The sialic acid content of
PMSG is high(Bourrlllon et al ,l959; Gospodarowicz,ì9ZZ) and small quantities
of glucose have been reported (Jutisz,l972).