Ultraviolet stimulated melanogenesis by human melanocytes is augmented by di-acyl glycerol but not TPA

Epidermal melanocytes (MC) synthesise melanin in response to ultraviolet radiation (UVR). The mechanisms mediating the UV‐induced activation of melano‐genesis are unknown but since UVR induces turnover of membrane phospholipids generating prostaglandins (PGs) and other products, it is possible that one of these might provide the activating signal. We have examined the effects of prostaglandins (PGs) E1, E2, D2, F2α, and di‐acyl glycerol upon the UV‐induced responses of cultured human MC and the Cloudman S91 melanoma cell line. The PGs had little effect on unirradliated cells and did not alter the response to UVR in either human MC or S91 melanoma cells. However, a synthetic analogue of di‐acyl glycerol, 1‐oleyl 2‐acetyl glycerol (OAG), caused a significant (P