Effects of retinoids on the cyclic AMP system of pig skin epidermis

Although retinoids reveal various biologic and biochemical activities on epidermal keratinocytes, their effects on the epidermal cyclic AMP (cAMP) system has been less well characterized. In order to elucidate the relation between them, an in vitro pig skin-slice incubation system was employed. After a long-term (up to 24 h) incubation in vitro, control skin responded to epinephrine only slightly. The addition of Ro 10-1670, an active derivative of Ro 10-9359 (etretinate) in the incubation medium, resulted in an increase of the beta-adrenergic adenylate cyclase response of epidermis. On the other hand, histamine-induced cAMP accumulation was decreased by the retinoid treatment after long-term incubation. The augmentation of the beta-adrenergic response was observed at 1 microM concentration and the maximal effect was observed at 10 microM. There was no significant difference in cAMP phosphodiesterase activities between the control and retinoid-treated skin. The effect was also observed by the addition of all-trans-retinoic acid, retinol, and Ro 10-9359; the latter two compounds revealed much lesser effects. The addition of combinations of various drugs (Ro 10-1670 and hydrocortisone; Ro 10-1670 and colchicine) resulted in more marked (additive or synergistic) effects than the single addition of each chemical. On the other hand, the addition of Ro 10-1670 and all-trans-retinoic acid resulted in neither additive nor synergistic effect, suggesting that they probably work on the same site. Our data indicate that the epidermal beta-adrenergic adenylate cyclase response is modulated by retinoids probably as an independent mechanism stimulated by glucocorticoids or colchicine.