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Paradoxical inhibitory effect of cromakalim on 86Rb outflow from pancreatic islet cells.

par Lebrun, Philippe ;Antoine, Marie-Hélène ;Devreux, V;Hermann, Marcel ;Herchuelz, André
Référence The Journal of pharmacology and experimental therapeutics, 255, 3, page (948-954)
Publication Publié, 1990-12

Article révisé par les pairs

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Résumé :

Cromakalim appears to be the most potent pharmacologic agent belonging to the new class of smooth muscle relaxants: the "K+ channel openers." The present study aimed at characterizing the effects of cromakalim on 86Rb outflow, 45Ca outflow and insulin release from prelabeled and perifused rat pancreatic islets. Cromakalim provoked a concentration-dependent reduction in 86Rb outflow. This inhibitory effect was attenuated in islets exposed throughout to glibenclamide or to a Ca+(+)-free medium. In islets exposed to glucose and extracellular Ca++, cromakalim induced a dose-dependent reduction in 45Ca outflow. The drug also inhibited the increase in 45Ca outflow mediated by K+ depolarization. Lastly, cromakalim elicited a concentration-dependent inhibition of insulin release from islets perifused in the presence of glucose and extracellular Ca++. The present data suggest that the paradoxical inhibitory effect of cromakalim on 86Rb outflow probably reflects the capacity of the drug to reduce the activity of the ATP-sensitive K+ channels and to indirectly inhibit the Ca+(+)-activated K+ channels. Furthermore, the cromakalim-induced changes in 45Ca outflow are compatible with an inhibitory effect of the drug on the voltage-dependent Ca++ channels.