THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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activity in the N-acetyl-lactosamine (NAf,) sy¡¿hetase assay,
it exhibited approximatety 4.58 of the potency of bovine
prolactin standard.
The molecular weight estinat.ed by BqLander et
al is 22,150 daltons with an isoelect,ric point is 5.9.
The amino acid conposition of bpL closely resembled that
of bcH and bPRL excepÈ for a higher content of serine and
glycine and a lower leucine content. By Outchlerlony
immunodiffusion, bpL forms 1ines of partia!. identity with
bcH against bGH antisera and with ovine placental lactogen
(oPL) against opl., antisera.
With the purified bpL, Bolander et aI (1976) have
developed a specific radioinununoassay for bpl,. Using t,his
RIA, they have quantitated the levels of bpl in the circulation
of beef and dairy cows. In both dairy and beef cows,
serum bPL levels remain low (less 50, ng,/ml) during the
first, tr{o trimesters and then rÍse rapidly between 160-2OO
days of gestat.ion to reach a plat.eau. The bpÎ., levels do
not declíne prior to parturit.ion. During Èhe last trimester,
serr¡n levels in dairy cor.rs. ll-031342 ng/mJ,, are signif icantly
higher than those in beef cattle, 65OtI3Z ng/mLi furthermore,
dairy cows with a higher milk production also tend to have
higher bPL levels. Serum levels are almost tbrice as high
in twin pregnancies and are not càrrelated with fet,al sex
or birth weight. The bpL levets in the nilk and amniotÍc
fluid fro¡n dairy catt.Ie during the last trimester are
approximately 86* and 258 of the serr¡m values, respectively,
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