In comparison, various experiments have been carried out in cyclic ewes, showing that total conceptus secretory proteins and/or purified IFN-t, or recombinant IFN were all able to significantly prolong luteal activity although to varying extents. Even at doses of IFN-т as low as 50 (xg/infusion per horn (twice a day) given in utero on Days 12-14, prolongation was significant. With high doses of recombinant IFN-т, a single intrauterine injection on Day 10 was sufficient to extend the maintenance of CL activity. Therefore, it is clear that the situation is different in cyclic gilts. buy ortho tri-cyclen online
We also checked that the infused doses had been delivered to the uterus. We first tested whether an adsorption of injected IFN could occur on the silastic catheter: IFN-т doses corresponding to Days 12, 13, and 14 were measured by antiviral assay before and after perfusion through a catheter of the same length as that used in vivo. No significant loss was found (data not shown). Second, the absence of trace amounts of IFN in plasma of treated gilts, especially at the highest doses (Table 1), as measured by ELISA, indicated that no blood leakage of exogenous IFN occurred in any gilt. We therefore assumed that the nominal doses were entirely administered in utero.