Mean (± sed) log10 progesterone production by granulosa cells after (A) 48 hours and (B) 144 hours in serum free culture supplemented with either 0, 5, 10 or 15 oocytes per well, 1 ng/ml pFSH and 100 ng/ml Long R3 IGF-1. Values are from 3 independent cultures, each treatment having 4 replicates. There was a significant effect of treatment (P < 0.001) on progesterone production at both time points. Bars with different superscripts are significantly different (P < 0.05). Morphological appearance of the organisation of granulosa cells around the oocytes when co-cultured under serum-free conditions: (C) granulosa cells supplemented with 10 oocytes per well and (D) granulosa cells supplemented with 5 oocytes. Scale bar represents 100 μm.