EFFECT OF CELL-PLATING DENSITY ON THE STEROIDOGENIC ACTIVITY OF HUMANCUMULUS CELLS

Expansion of the cumulus mass results in dilution of cumulus cells in accumulated hyaluronic acid. This process is associated with an increa se in progesterone secretion. The present study was carried out to eva luate the relationship between these two processes in vitro. Dilution of human cumulus cells was attempted by changing the cell-plating dens ity of cumulus cells in culture. Concurrent with an increase in cell-p lating density from 0.25 x 10(4) to 8 x 10(4), progesterone secretion increased by 10.5 times (P < 0.001), 9 times (P < 0.001), and 5.9 time s (P < 0.001), and oestradiol secretion increased by 1.4 times (P < 0. 001), 1.1 times (P > 0.05), and 2.6 times (P < 0.005) during days 0-3, 3-5, and 5-7 of culture, respectively. However, when steroid secretio n was expressed in terms of ng per number of cells, the increase in ce ll-plating density from 0.25 x 10(4) to 8 x 10(4) coincided with a dec rease in progesterone secretion of 3 times (P < 0.001), 3.5 times (P < 0.001), and 5.4 times (P < 0.005), and oestradiol secretion decreased by 23 times (P < 0.001), 30 times (P < 0.001), and 12.5 times (P < 0. 001) during days 0-3, 3-5, and 5-7 of culture, respectively. The proge sterone:oestradiol ratio increased gradually with the increase in cell -plating density. However, at the higher range of eel-plating density the progesterone: oestradiol ratio decreased with extension of the cul ture period. Addition of human FSH (hFSH) or hCG increased progesteron e secretion when the cumulus cells were plated at 2 x 10(4), but in mo st cases not at 0.25 x 10(4) or 8 x 10(4) cells per dish. However, bot h hFSH and hCG decreased oestradiol secretion at 2 x 10(4) cells per d ish. In the presence of gonadotrophins, an increase in cell contact an d cytoplasmic processes during days 0-3 and 3-5 was noted. This study indicates that secretion of progesterone and oestradiol per number of cells is significantly increased with a decrease in cell-plating densi ty. Furthermore, addition of gonadotrophin increased progesterone and decreased oestradiol secretion at the middle range of cell-plating den sity.