We have devised a new in vitro model of type I cutaneous anaphylaxis. Male albino rats were sensitized with DNP-Ascaris. Abdominal skin was shaved, and thin, split-thickness slices of skin were cut with a dermatome. The dermis was excised and cut into 100 mg pieces. The dermal tissue was incubated with antigen in Tyrode's solution for 30 min at 37 degrees C. Antigen-induced histamine release from dermal tissue was measured fluorimetrically. Using this system, we measured histamine release from PUVA-irradiated and non-irradiated dermal tissues. A single PUVA irradiation inhibited type I cutaneous anaphylaxis, but did not affect spontaneous histamine release or total dermal histamine. Our model is considered to be useful for investigation of the mechanism of suppression of type I cutaneous anaphylaxis by PUVA.
Ultraviolet-B and PUVA share several biological events with phorbol ester tumor promoters. The effects of ultraviolet-B irradiation and topical PUVA treatment on ornithine decarboxylase activity, DNA synthesis, and protein kinase C activity, which are known to be induced or activated by phorbol ester tumor promoter, were investigated in hairless mouse skin. Ornithine decarboxylase activity was remarkably enhanced by ultraviolet-B and PUVA. Although PUVA did not affect DNA synthesis significantly, ultraviolet-B stimulated epidermal DNA synthesis approximately 5-fold over control values at 48 h. However, unexpectedly, neither cytosolic nor membrane-bound protein kinase C activity showed any change during the 2 h after either treatment. These results suggest that the protein kinase C system is not involved in the initial signal transduction system of ultraviolet-B or PUVA, unlike the case with phorbol ester tumor promoter.
To investigate the influence of ageing on wound healing, we cultured fibroblasts derived from human dermis in type I collagen gel, and evaluated the relationship between gel contractility and ageing. Cells were obtained from children (0-15 years old, Group A), early adulthood (16-40 years old, Group B), mid-adulthood (41-60 years old, Group C), and the elderly (61 or older, Group D). Gel contractility was determined by measuring the diameter on the second day after gel preparation. Within the tenth passage, gel contraction was the most marked in Group A, but did not differ among the other groups. Gel contraction at passages 30-40 did not differ from those within the tenth passage in Groups B, C and D, but it decreased markedly in Group A to a value similar to that in the other groups. These results show that fibroblasts in childhood are more contractile than those in adulthood and are more readily affected by passages (in vitro ageing).
