Human granulosa cells are a site of sulphatase activity and are able to utilize dehydroepiandrosterone sulphate as a precursor for oestradiol production.

Dehydroepiandrosterone sulphate (DHEAS) is the most abundant androgen in the circulation and in ovarian follicular fluid. A steroid sulphatase accepting DHEAS as a substrate has been identified in the follicle, but the cellular location has not been determined. As DHEAS is also a potential source of oestrogen for endocrine-dependent tumours, a potent steroid sulphatase inhibitor oestrone-3-O-sulphamate (EMATE) has been developed which inhibits this activity in rat liver and mammary tumour. The aim of this study was to investigate human granulosa cells as a site of steroid sulphatase activity, to determine whether DHEAS can be utilized as a precursor for oestrogen synthesis and to investigate the inhibitory capacity of EMATE in these cells. Conversion of DHEAS to DHEA was assessed in luteinized granulosa cells by tritiated steroid assay following incubation with or without LH or insulin and steroid accumulation in the medium measured by RIA. The effects of EMATE were assessed by addition of a range of doses during the measurement of conversion of DHEAS to DHEA. Cells from three sizes of small follicles from an unstimulated ovary were also assessed for their ability to produce oestradiol from DHEAS. Sulphatase enzyme activity was present in all cells; the mean conversion of tritiated DHEAS to DHEA was 50% (range 4-65%). LH and EMATE inhibited and insulin stimulated this activity. Addition of DHEAS to granulosa cells caused a dose-dependent increase in oestradiol and androstenedione production with no change in progesterone concentration. LH increased the accumulation of oestradiol in the medium. DHEAS also stimulated oestradiol production by granulosa cells from small follicles. This is the first demonstration that granulosa cells are a site of sulphatase activity and that DHEAS can be utilized as a substrate for androstenedione and oestrogen production. This may be of physiological importance for both normal folliculogenesis and oestrogen-dependent tumour growth.