Effects of an ultraviolet B radiation absorber on photocarcinogenesis in hairless albino mice.

Uvinul T 150, a UVB absorber, was administered (concentration 5%) in a vehicle to the skin of hairless albino mice before ultraviolet radiation (UVR) exposure for 5 days per week in a photocarcinogenicity study. Uvinul T 150 prolonged the latency period to 50% skin tumor incidence (controls: 21-22 weeks; Uvinul T 150: 36 weeks in males and 31 weeks in females). When Uvinul T 150 was applied in an alternating-exposure procedure (3 days/week before and 2 days/week after UVR), the inhibition of photocarcinogenesis was less marked (latency period 28-30 weeks). The vehicle formulation had no effect (latency period 20-21 weeks). The sensitivity of the test system was demonstrated by a positive control (8-methoxy-psoralene). Although UVB absorption was shown to inhibit photocarcinogenesis, the results also suggest that UVA radiation makes a contribution to skin tumor formation.