Role of protein kinase C in cholinergic stimulation of lacrimal gland protein secretion

The purpose of this study was to determine the role of protein kinase C (PKC) isozymes in carbachol-induced protein secretion in the lacrimal gland. Three isoforms of PKC are present in rat lacrimal gland; PKC-alpha, -delta and -epsilon. Carbachol translocated PKC-epsilon during 5 s incubation. Pretreatment with PdBu for 0 to 4 h down-regulated PKC-alpha by 31% at 20 min, PKC-epsilon by 36% at 2 h, and PKC-delta by 37% at 4 h. A 2 h phorbol ester treatment inhibited carbachol-induced secretion completely at 1 min and partially at 5, and 20 min, but did not alter the carbachol-induced increase in the intracellular [Ca2+]. We conclude that PKC-alpha and -epsilon, but not PKC-delta, are implicated in cholinergic agonist-induced protein secretion in rat lacrimal gland.