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J. Gierow, M.C. Edman, S.V. Andersson, E.C. Sjogren, D. Delbro; Purinergic Modulation of Lacrimal Gland Acinar Cell Secretion . Invest. Ophthalmol. Vis. Sci. 2003;44(13):2512.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Lacrimal gland secretion has been studied in several laboratories for a number of years. However, it has become increasingly clear that purine compounds may play a mediator role for exocrine secretion (Clin. Exp. Pharmacol. Physiol. 13: 425, 1986; Crit. Rev. Oral Biol. Med.10: 210, 1999). Therefore, it is of interest to study the effect of purines and related compounds on lacrimal gland secretion, their modulatory effect on regulated secretion, and the purinergic receptors present. Methods: Rabbit lacrimal gland acinar cells were prepared according to our standard procedure (Am. J. Physiol. (Cell Physiology) 271: C1685, 1996). Isolated single cells were placed in a serum-free culture medium on standard culture plates coated with Matrigel and the cells were allowed to re-establish their acinus-like structures by culturing for two days. Secretory capacity of the cultured cells was measured by pre-incubation for 30 min at 37°C with buffer alone, followed by incubation for an additional 30 min at 37°C w./w.o. 0.1 mM carbachol or other secretagogues. Basal secretion and regulated secretion was determined enzymatically as secreted beta-hexosaminidase activity, using the 4-methyl umbelliferyl conjugate as substrate. Sectioned tissue was analyzed for receptor presence by immunohistochemistry using an antibody against the purinergic A1-receptor. Results: Carbachol alone resulted in a more than 7-fold increase of secreted beta-hexosaminidase activity, whereas both VIP and 0.1 mM adenosine resulted in a less than 2-fold increase over basal secretion. An almost10-fold increase in secretion was observed when carbachol and VIP was combined whereas combinations of carbachol and adenosine resulted in more than 10-fold increase. Cyclopentyladenosine, an A1 specific agonist, had similar effects as adenosine. In addition, preliminary results from immunohistochemistry indicated the presence of an A1-receptor in rabbit lacrimal gland tissue. Conclusions: Our data indicate the presence of an A1-receptor both in tissue and cultured cells. Adenosine alone, had only a small effect on secretion, but a significant increase was observed when combined with carbachol indicating a synergistic effect. We therefore propose a modulatory role for the adenosine A1-receptor in the lacrimal gland, and our laboratory is currently investigating the presence and role of other purinergic receptors in the lacrimal gland.
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