Abstract
The stimulatory effect of forskolin on amylase secretion was studied by pretreating rat parotid tissue with forskolin for 10 min, incubating it in medium without forskolin for 10 min, and then treating it with forskolin again. Pretreatment with 10 μM forskolin for 10 min resulted in increased amylase secretion and enhanced accumulation of cyclic AMP in the tissue during the second incubation with forskolin. In the presence of colchicine or vinblastine, the enhancement in cyclic AMP accumulation during the second incubation with forskolin was prevented, but the increased amylase secretion remained unchanged. The increased amylase secretion was counteracted only in the presence of concanavalin A. On the other hand, increased amylase secretion induced by isoproterenol (IPR) pretreatment was counteracted by colchicine, vinblastine, concanavalin A or strychnine. These data suggest that the total amount of cyclic AMP in the tissue does not have any essential role in the supersensitivity of the amylase secretory response, and that the supersensitivity induced by forskolin differs from that induced by IPR.
