December 1987
Volume 28, Issue 12
Free
Articles  |   December 1987
Effects of inorganic ions on rabbit ciliary process adenylate cyclase.
Author Affiliations
  • T W Mittag
    Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029.
  • A Tormay
    Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029.
  • M Ortega
    Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029.
  • S M Podos
    Department of Ophthalmology, Mount Sinai School of Medicine, New York, NY 10029.
Investigative Ophthalmology & Visual Science December 1987, Vol.28, 2049-2056. doi:
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      T W Mittag, A Tormay, M Ortega, S M Podos; Effects of inorganic ions on rabbit ciliary process adenylate cyclase.. Invest. Ophthalmol. Vis. Sci. 1987;28(12):2049-2056.

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      © ARVO (1962-2015); The Authors (2016-present)

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Abstract

The interaction of several inorganic ions (Mn2+, Ca2+, VO3-, and F-) with adenylate cyclase in the albino rabbit ciliary process particulate fraction was studied. Effects of these substances were determined on three activity states of the enzyme (basal, Gs-protein stimulated activity via isoproterenol activation of beta-adrenergic receptors, forskolin-activated catalytic unit) in the presence of 3 mM Mg2+, 1 mM EDTA and 0.2 mM EGTA. A different pattern of effects was found for each of the four ions. Addition of Mn2+ (2 mM) increased all three responses; basal by up to ten-fold, isoproterenol and forskolin by four to five-fold. Added Ca2+ (1 mM) increased basal by two to three-fold, but inhibited isoproterenol and forskolin responses by 25-50%. Added vanadate (1-10 mM) increased basal by two to four-fold, had no effect on the isoproterenol response, but doubled the forskolin response at 3 mM. Added F- (10 mM) increased basal by 30-40-fold, decreased the isoproterenol response and potentiated the forskolin response. The response to F- which directly activates G-proteins was much greater than that of non-hydrolysable GTP analogs, which also directly activate G-proteins. The results suggest that more than one type of adenylate cyclase and/or several modes of regulation of adenylate cyclase with different ionic requirements may be present in ciliary process membranes.

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