THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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SECTION VII SUMMRY
In surmary, we have been successful in pur.lfying
ovine placental 'lactogen from ovine placentaì cotyledons. Blnding
studies of oPL on ovine tissues showed that the distribution
of binding sites for opl are .located on l.lyer(maternal and fetal),
adipose tissue, ovary, corpus .luteum, and non_pregnant uterus.
Kinetic anaìysis showed that the binding of opl to the receptor
occurs readily at physlological concentrations of the hormone.
Specificity studies showed that only growth hormone proparations
could dlsplace opL binding to Ìts receptor sites whereas other
hormone preparations could not, indicating that opl binds specìflcally
to GH-receptor sites in the sheep tissues.By empìoylng the radio_
receptorassay for pìacental lactogen us.ing opl and sheep ìiver as
hormone standard and receptors respective.ly, pìacental .lactogens
were detected in the placental extracts of human, nonkey, goat,
guinea pig, and mousa. placeritat .1aòtogen could-not be
dòtected-in placental, àxtracts of pig, doo,. horse, cow, rat,
and rabbit.
.A soecjfic homologous rad i ofmmunoas say for opl(RIA_opL)
has, been deve'loped. The assay is specific for opl in that opRL,oGH,
and as well as other hormones includ.lng rat, caprine, bovine, monkey
and hPL exhibited no cross-reaction in the assay. Util.izlng this RIA,
oPL is detected in uterine vein blood samples as earìy as 25 days
of gestation. The secretory pattern of opL is similar to that
of human and monkey placentar ìacùogen. opL Ís found rn the