Abstract
Effects of colchicine on the epidermal adenylate cyclase systems were investigated. When pig skin (epidermis) was incubated in RPMI 1640 medium without the addition of serum, the beta-adrenergic adenylate cyclase response (epinephrine-induced cyclic AMP accumulations) gradually decreased, whereas adenosine and histamine responses remained high or increased during the long-term (up to 48 h) incubation period. The addition of colchicine (1 mumol/liter) in the incubation medium resulted in an increase in the beta-adrenergic responsiveness and a decrease in adenosine and histamine responsivenesses. The effects of colchicine were both time- and concentration-dependent; they could be observed after 9-12 h incubation, and the maximal effect was obtained at a concentration of 0.1 mumol/liter. Similar effects were observed by the addition of another microtubule-disruptive agent, vinblastine. On the other hand, cytochalasin B, which affects the microfilament system, apparently decreased the beta-adrenergic response and increased adenosine and histamine responses during the long-term incubation period. The addition of serum in the incubation medium resulted in essentially the same effect as that of colchicine; in the presence of serum, colchicine-treated skin responded much more markedly to epinephrine (and much less to adenosine and histamine) than the control skin after 24- and 48-h incubation. Previously we reported that hydrocortisone has similar potentiating effects on the beta-adrenergic system of epidermis. The comparison of the effects of both compounds revealed that colchicine had a stronger effect than hydrocortisone, and furthermore, the simultaneous addition of both compounds (colchicine and hydrocortisone) in the incubation medium resulted in the more marked increase of beta-adrenergic response than the single addition of each chemical. Our overall results, coupled with the finding that hydrocortisone has no toxic effects on the adenosine- or histamine-adenylate cyclase system of epidermis, suggest that colchicine affects epidermal adenylate cyclase systems probably through a mechanism that is independent of glucocorticoid (hydrocortisone) effect.
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