A stimulatory role of protein kinase C in feline tracheal submucosal gland secretion

Abstract

To determine the role of protein kinase C (PKC) in airway submucosal gland secretion, we examined the effect of a selective PKC stimulant, phorbol 12-myristate 13-acetate (PMA), on mucus glycoprotein (MGP) secretion, fluid secretion and intracellular Ca 2+ concentration ([Ca 2+]i) in isolated feline submucosal glands. MGP and fluid secretions were estimated by measuring trichloroacetic acid (TCA)-precipitable glycoconjugates and 22Na-efflux, respectively, from isolated glands. [Ca 2+]i was measured using a Ca 2+-sensitive fluorescent dye, Fura 2. PMA itself produced a significant increase in MGP secretion in a dose-dependent fashion (173% of control at 10 −5 M). PMA also produced a significant increase in 22Na-efflux (151% of baseline rate constant at 10 −5 M). Indomethacin failed to alter the increase in MGP secretion or in 22Na-efflux in response to PMA. Two PKC inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H-7) and sphingosine, inhibited both MGP secretion and 22Na-efflux stimulated by PMA; there was only a partial inhibition after stimulation by methacholine (MCh). PMA did not significantly alter [Ca 2+]i and H-7 did not alter the MCh-induced [Ca 2+]i rise. These findings indicate that PKC has a direct stimulatory role in stimulus-secretion coupling of airway submucosal gland secretion.