THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

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(l ) aséay of gror^¡th prorqoting activity in hypophysectomj-zed
fats-
The tibia test for growth pronoting activity was
performed by the Endocrine I, aboratories of MadisonfInc.,
Wisccinsin 53713, U.S.A. The experimental procedures for the
assay are the following:
In¡nature Sprague ÈDatdley rats vrere hypophysectonized
at 30 days of age and held for 12 days under closely regulated
conditions of temperature and humiility. At thê end of thìs t2 day
acclÍmatization period, anímal.s exhibitÍng inappropriate weight
gain were dÍscarded. partÍally purified opl, ( ct{ Fotencry G.O - 1.3
Ãu/nç,) estimated by RRA-GH using hcH ¿is standard) or bovine
growth hornone ( 0.9 IU,/mg ) , were þrepared for injection
using equal- vol-umes of chiLl_ed saLine (0.9t NaCl) arid 0.05 M
ammonium bicarbonate, pH Z.B. If necessary, diluted NaOH
(0.01N) was added to dissolve the hormone preparations but
the final" pH rùas never greater than 9.5. The solut.ions
containing saline, opL or bGH were administered by lntraperitoneal
injection once daily for 4 days. The anímals lvere
sacrificed by decapitation on the day foltoriing the lâst day
of injection. Both tibae of each rat. were dissected, split
longitudinally and prepared for measurement, of epiphyseal
width. !{eight.s of adrenals and ovaries vrere recorded. The
potency estirnates of, opL were caLculated statistically using
bGH (0.9 IU.mg) as standard.