PURPOSE: Lacritin protein is highly expressed in the lacrimal gland, secreted 
into tear fluid, and detected only in primates. The mechanism for lacritin 
secretion has not been fully investigated, because a system for culturing 
primate lacrimal acinar cells had not been established. The purposes of the 
present study were (1) to develop a procedure to culture lacrimal acinar cells 
from monkey and (2) to determine the mechanism for the secretion of lacritin in 
the culture system.
METHODS: Acinar cells from monkey lacrimal gland were cultured and 
characterized. Lacritin and other proteins were detected by 
immunohistochemistry, immunocytochemistry, and immunoblot analysis. Secreted 
proteins were also detected in the medium from stimulated acinar cells. mRNAs 
were determined by microarray and qPCR. Intracellular calcium levels were 
measured by calcium-4 assay.
RESULTS: Acinar cells cultured for 1 day contained adequate amounts of lacritin, 
lactoferrin, and lipocalin for use in lacritin secretion studies. The 
cholinergic agonist carbachol (Cch) stimulated the secretion of lacritin and 
increased intracellular Ca2+. Cch-induced lacritin secretion was inhibited by 
the store-operated calcium (SOC) channel inhibitor YM58483 and the PKC 
inhibitors GF109203 and Ro-32-0432. Cch-induced lacritin secretion was not 
inhibited by MAPKK inhibitor U0126, although p42/p44 MAPK was phosphorylated. 
Cch also enhanced gene transcription, which was inhibited by U0126, GF109203, 
and calcium chelators.
CONCLUSIONS: Successful culture of monkey lacrimal acinar cells showed that, 
among the prevalent tear proteins, the secretion of lacritin involved the 
PKC/Ca2+ pathway, not the p42/p44 MAPK pathway. Induction of transcription by 
Cch involved the independent p42/p44 MAPK and PKC pathways.