THE UNIVERSITY OF MANITOBA STUDIES ON OVINE PLACINTAL ...

3. RecêÞtoÏ assayÊ:
102
Ois-placeinent-.. ,cuf¡¡ês , of opf, in the radioreceptorassay for
prolactin (RRÃ-.PRL) and for growth hormone (RRa*6¡¡ ¡ ¡rere determined
using rabbit mamrnary gland and liver respectìveìy_
The purified oPt preparation lùas accurately weighed
and dissolved in 0.05M ammonium bicarbonate solution. Serial
dilutions of opL were made in 0.025M Tris-HCl , pH?.6 containing
0.1S BSA. The radioreceptorassay for proLact,in (RRA-pRL) was
performed according to the method of Shiu et aL(1973) as
described previously. The radioreceptorassay for growth hormone
was performed according to the method of Tsushima et al- (19?3)
as described previously except. that [125r]-iodo oGH and ocH
(NIH 0-986L, 2.0 ItJ/mg) were used as tracer and standard
respectively.
[125r]-iodo ocu was prepared by the lactopero xidase
enzymat,ic fl¡ethod described by ThoreII and Johannson(1971)
with slight modification. During iodination, the pH of 0.05M
phosphate buffer added in the react,ion mixture is pH 7.0,
5 ug of lactoperoxidase, 10 uI of 30t hydrogen peroxide
(1:1,500 dilutíon), and reaction period of 20 min. were
used. The percentage of radioreactivity incorporated was
55-60, and the specific activity was 100-l-30uCí/ug of protêin.