Can fluid from early rabbit embryos stimulate progesterone secretion in monkey ovarian cells?

Details

This laboratory experiment tested whether fluid from rabbit blastocysts could stimulate progesterone secretion in cultured monkey ovarian granulosa cells. Fluid was aspirated from Day 6½–7 rabbit blastocysts and added to cultures of granulosa cells obtained from preovulatory follicles of untreated rhesus monkeys or from follicles of PMSG-treated monkeys.

The researchers measured the stimulation of progesterone secretion and equated it with that produced by hCG. They also measured hCG-like activity with a radioreceptor assay using 125I-labelled hCG and porcine granulosa cells.

In 8 out of 10 experiments with cultured cells from untreated monkeys, adding 20% blastocyst fluid during Days 6–9 of culture stimulated progesterone secretion 2- to 6-fold. Similar findings were obtained in five experiments with cultures from PMSG-treated monkeys, except that the fluid was added during Days 0–6 of culture. The granulosa cells in these cultures underwent morphological luteinization.

Compared with a purified hCG standard, the blastocyst fluid contained about 0.76–2.5 ng of hCG-like activity/ml; this activity was non-dialysable. The radioreceptor assay indicated 0.5–2.5 ng of hCG-like material/ml.