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Involvement of Calcium in the Regulation of Serotonin N ‐Acetyltransferase in Retina
Author(s) -
Iuvone P. Michael,
Besharse Joseph C.
Publication year - 1986
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.1986.tb12928.x
Subject(s) - divalent , calcium , trifluoperazine , chemistry , retinal , nifedipine , retina , biophysics , xenopus , nat , biochemistry , endocrinology , biology , medicine , neuroscience , calmodulin , computer network , organic chemistry , gene , computer science
The possible involvement of calcium in the regulation of retinal serotonin N ‐acetyltransferase (NAT) activity was investigated using eye cups of Xenopus laevis cultured in defined medium. Omitting CaCl 2 from the culture medium completely inhibited the dark‐dependent increase of NAT activity at night. Approximately 10 −4 ‐10 −3 M free Ca 2+ was found to be required for the maximal increase of NAT activity in the dark. Other divalent cations—Ba 2+ , Sr 2+ , and Mn 2+ —did not substitute for Ca 2+ . Antagonists of voltage‐sensitive calcium channels, including nifedipine, methoxyverapamil (D600), Co 2+ , and Mg 2+ , were found to be effective inhibitors of the dark‐dependent increase of retinal NAT activity. Trifluoperazine also decreased retinal NAT activity. These studies indicate that the increase of retinal NAT activity in the dark is mediated by a specific Ca 2+ ‐dependent process and that Ca 2+ influx through voltage‐sensitive calcium channels is involved.