Observations on preovulatory human ovarian follicles and their aspirates.

During laparoscopy for the collection of preovulatory oocytes the ovaries were inspected and the numbers of Graafian follicles were counted. Most patients had one large preovulatory follicle but three patients had two and might have had twin ovulations. The large follicle was in the left ovary in 9 patients and in the right ovary in 11. It could be aspirated easily in most patients, viscous follicular fluid, presumably rich in hyaluronic acid, appeared to accumulate in preovulatory follicles between 18 and 27 hours after the luteinizing hormone surge. The content of steroids in follicular fluids indicated that the largest follicle was preovulatory in most patients, the smaller follicles being non-ovulatory. Granulosa cells aspirated from the large preovulatory follicles were active on the delta 4 pathway and able to aromatise androgens to oestrogens, but did not undertake conversions on the delta 5 pathway.