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  • Title: Expression of adenylate cyclase subtypes II and IV in the human outflow pathway.
    Author: Zhang X, Wang N, Schroeder A, Erickson KA.
    Journal: Invest Ophthalmol Vis Sci; 2000 Apr; 41(5):998-1005. PubMed ID: 10752933.
    Abstract:
    PURPOSE: It has been demonstrated that low doses of pilocarpine and other muscarinics substantially increase outflow facility in the isolated human outflow system devoid of ciliary muscle. These cholinergic-induced facility responses were thought possibly to be due to elevation of cAMP as a result of the presence of adenylate cyclases II (AC-II) and IV (AC-IV). Therefore, whether these isoforms are present in outflow tissues was examined. METHODS: Human anterior segments were perfused with carbachol (10(-9)-10(-5) M), and outflow facility and cAMP levels in the perfusate were measured simultaneously. Isolated trabecular meshwork (TM) were incubated with carbachol (10(-7) M), and the subsequent changes in cAMP were measured by radioimmunoassay. AC-II and AC-IV were characterized in ocular tissue with reverse transcription-polymerase chain reaction and in situ hybridization. RESULTS: Outflow facility increased, in a dose-dependent manner, by 10%, 16%, and 27% in response to 10(-9), 10(-7), and 10(-5) M carbachol, respectively. Similarly, cAMP increased by 9%, 70%, and 210% in response to 10(-9), 10(-7), and 10(-5) M carbachol, respectively. In addition, cAMP levels significantly increased by 39% in isolated TM strips incubated with 10(-7) M carbachol. AC-II was detected in most normal tissue examined, but not in any cultured cell lines or any glaucomatous tissue. AC-IV was also widely expressed in most normal tissues, faintly detected in some glaucoma tissue, but not detected in most cultured cells. CONCLUSIONS: The presence of AC-II and AC-IV in outflow tissues supports the hypothesis that cholinergics may indeed exert an effect on outflow facility, mediated by cAMP, which is independent of muscle contraction.
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