THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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and monkey placental lactogen, except that primate pls do not
decline until partu ri ti on (Bel anger et al ,.l97.l ; Spelìacy et al ,l972).
The oPL concentrations during pregnancy, measured
by radioìnrnunoassay, cannot be compared quantitively with the oPL
concentrations previousìy reported by rad.loreceptor assay ( felly
et al ,1974; Djiane et al ,197b; Handwerger et al ,1975) since
purifìed oPL and l2sl-opl were not used in the rad.ioreceptor assays.
Handwerger et al (197S) reported that the opl concentrations during
pregnancy measured by rad i oreceptoras say were about tw.lce those
measured by radio inrmunoassay. However, Jn their study, purified hpL
rather than oPL was used as standard und ì251-hpnL was used as
tracer in the radioreceptor. assay. Usìng l25I-opRL as tracer
and oPRL as standard in the manrnary gìand receptor assay, Kelly et a1
(]974) noted peak oPL concentrations of about '1000-2000 n9/m'l in
three ewes durìng pregnancy and Djiane et a.t'(1975) noted peak opl
concentrations of about 300 and 900 nglml in two pregnant ewes.
Kelly et al (1974) and Djiane et al(197S) aìso noted wide variation
in rnaternal oPL concentrations in the latter half of pregnancy and
a decrease in oPL concentrations just before parturition,
It is interesting that the concentration of opl in
fetal sera is nine times higher than that .in maternal peripheral
sera from day 47-70. Although human pL and monkey pL are also found
in the fetal circulation (Kaplan et al ,1965; Friesen l97l), there
are no reports that fetal PL levels are ever higher than materna.l
levels. Furthermore, there is almost no lnformation avai'lable