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J.P. Gierow, M. Edman, S.V. Andersson, E.C. Sjögren, D. Delbro; Adenosine Receptors In The Rabbit Lacrimal Gland And Their Effects On Secretion. . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3860.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: We have previously shown, in preliminary studies (Invest. Opthalmol. Vis. Sci. 44: a2512, 2003), that an A1 adenosine receptor is present in lacrimal gland acinar cells and increases secretion when activated. In the present study, we have confirmed our earlier results using A1 specific agonists and antagonists in combination with RT–PCR. The presence of another adenosine receptor has also been studied using a similar approach together with immunohistochemistry. Methods: Rabbit lacrimal gland acinar cells were prepared according to our standard procedure (Am. J. Physiol. (Cell Physiology) 271: C1685, 1996) yielding single cells that were placed in a serum–free culture medium on standard culture plates coated with Matrigel and cultured for two days. Secretory capacity was measured after a pre–incubation for 30 min at 37 ºC with buffer alone, followed by incubation for an additional 30 min at 37 ºC w./w.o. the presence of secretagogues. Basal secretion and regulated secretion was determined enzymatically as secreted beta–hexosaminidase activity. Cultured cells were analyzed for receptor presence by immunohistochemistry using antibodies against purinergic A1– or A2A–receptors. Primers for RT–RCR were designed from already reported sequences and used for determination of receptor message in rabbit lacrimal tissue. Results: Both adenosine and cyclopentyladenosine, an A1 specific agonist, increased secretion 2–fold by themselves, and an almost 10–fold synergistic increase was observed when combined with carbachol. Both these effects were inhibited by an A1 specific antagonist, 8–phenyltheophyllin. Secretion was also stimulated by an A2 specific agonist, cyclopropylcarboxamidoadenosine, with similar results. In addition, results from immunohistochemistry and RT–PCR indicate the presence of both an A1– and an A2A– receptor in the rabbit lacrimal gland. Conclusions: Our results indicate the presence of an A1–receptor in rabbit lacrimal gland pharmacologically, by immunohistochemistry and by RT–PCR. The receptor acts synergistically with the cholinergic receptor, but the molecular mechanism remains to be elucidated. Pharmacological evidence and immunohistochemistry also indicate the presence of an A2A–receptor and this is preliminary supported by RT–PCR
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