Partial purification of a luteotrophic substance from bovine fetal cotyledon granules. 
To determine whether luteotrophic activity is present in the bovine placental granules, fetal cotyledons from fetuses of 50-100 days of gestation were used.  Enriched granules were prepared using a Percoll gradient.  Active substances were obtained from the granules by freeze-thawing.  The extracts thus obtained were then eluted on a Sephacryl S-300 column.  The resultant fractions were then analysed by (1) a radioreceptor assay for hCG-like substances and (2) a bioassay using progesterone production by bovine luteal cells.  There were two peaks of activity, one indicative of a high molecular weight substance and the second of a low molecular weight substance.  Higher molecular weight substances were eliminated by using acidic extracts.  The low molecular weight fraction was further analysed using reverse phase h.p.l.c. ( acetonitrile:water gradient).  The elution of this substance at 45% acetonitrile resulted in a 100-fold increase in luteotrophic activity in the bioassay compared to the Sephacryl fraction.  The small molecular weight substance is heat-stable and not extracted to the organic phase when partitioned between methanol and chloroform.