76 JOURNAL OF THE SOCIETY OF COSMETIC CHEMISTS UV 0 2 6 10 12 UV 0 2 6 10 12 UV 0 2 6 10 12 Boehmlte % Boehmlte % Boehmlte % 7 day 13 day 22 day Figure 9. Preventive effect of MDC-boehmite complex (MDC 6%, boehmite 0-12%) on UVB-induced hyperpigmentation of tortoiseshell guinea pig skin as revealed by color difference. The experimental an- imals were treated (2 mg/cm 2) with samples consisting of MDC-boehmite aqueous solution on five separate areas and ten minutes later were irradiated for five minutes with an SE lamp (1.4 mW/cm2). This process was repeated daily for three days. n = 7. AL = color difference. 7OO 2OO IOO 0 uv 6-0 6-2 6-6 6-10 6-12 c MDC/Boehmlt• % Figure 10. Effect of MDC-boehmite complex (MDC 6%, boehmite 0-12%) on the increased melanocyte population induced by UVB radiation.

A NEW BROAD-SPECTRUM SUNSCREEN 77 inhibitory effect of sunscreens on the amount of prostaglandin E 2 released from irra- diated skin, the flank skin of guinea pigs was treated with PUVA with or without the prior application of MDC-boehmite at 6% concentration. Released amounts of prosta- glandin E 2 significantly increased after PUVA treatment with 2.25 MED dose and reached three times the level in nonexposed areas. The prior application of MDC- boehmite complex markedly suppresses the release of prostaglandin E 2 up to the nonex- posed level in all mixture ratios (Figure 11). In the same PUVA treatment, the prior application of MDC-boehmite (1/1) + Parsol MCX (UVB sunscreen) with several combinations also markedly suppressed the release of prostaglandin E 2 up to the nonexposed level except in the absence of MDC-boehmite, which shows no release or weak inhibition of release (Figure 12). PREVENTIVE EFFECT OF MDC-BOEHMITE COMPLEX ON PROSTAGLANDIN E 2 RELEASE INDUCED BY UVB The flank skin of guinea pigs was irradiated by UVB at the 2 MED dose with or without the prior application of MDC-boehmite at the 6% concentration. Released amounts of prostaglandin E 2 significantly increase after UVB irradiation and reach 2.5 times the level of nonexposed areas. Prior application of MDC-boehmite complex mark- edly suppresses the release of prostaglandin E 2 up to the nonexposed level in all mixture ratios (Figure 13). (n•/•ml) U¾ 6-0 6-2 6-6 6-10 •-12 C U¾ 6-0 6-2 6-6 6-10 6-12 C MI)C/Bo•hmite % MI)C/Boehmlte % 2 hr poeUrradlaUon 24 hr posUrradiation Figure 11. Effect of MDC-boehmite complex (MDC 6%, boehmite 0-12%) on prostaglandin release in the medium of organ-cultured skin after exposure to PUVA. Hartley white guinea pigs received 4.2 mg/kg body weight of 8-methoxypsoralen in 30% ethanol intraperitoneally. Thirty minutes after administration, they were exposed to UVA of 3.5 mW/cm 2, emitted from Toshiba FL20BLB lamps. The samples, con- sisting of MDC-boehmite aqueous solution, were treated (2 mg/cm 2) ten minutes before irradiation. Irra- diated or nonirradiated skin was cut off at indicated hours postirradiation to assay the PGE 2 release in the medium of the organ culture. n = 3.