Oestrogen production by individual follicles explanted from ovaries of sheep.

Ovarian follicles are a major site of oestrogen synthesis in sheep, but almost nothing is known about the relative contribution made by follicles of different sizes to the output of oestrogen at various stages of the reproductive cycle. To determine this, ovaries were dissected from sheep, all follicles over 2 mm in diameter were explanted separately as organ cultures and the daily production of oestrogen from each follicle was measured. This study was preceded by a series of preliminary experiments undertaken to define suitable conditions in which ovarian follicles would retain both their morphological integrity and steroidogenic capacity in culture. The 224 follicles used in the preliminary series of experiments were explanted from the ovaries of seventeen sheep killed between the 2nd and 15th days of the oestrous cycle. A total of 218 follicles was used in the main experiment: 186 follicles were obtained from seventeen sheep during the oestrous cycle, seventeen follicles from two sheep at mid-pregnancy and fifteen follicles from