Involvement of calcium in the regulation of serotonin N-acetyltransferase in retina.
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 CaCl2 from the culture medium completely inhibited the dark-dependent increase of NAT activity at night. Approximately 10(-4)-10(-3) M free Ca2+ was found to be required for the maximal increase of NAT activity in the dark. Other divalent cations--Ba2+, Sr2+, and Mn2+--did not substitute for Ca2+. Antagonists of voltage-sensitive calcium channels, including nifedipine, methoxyverapamil (D600), Co2+, and Mg2+, 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 Ca2+-dependent process and that Ca2+ influx through voltage-sensitive calcium channels is involved.
P M
PM
Iuvone
J C
JC
Besharse
D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D001191:Arylamine N-Acetyltransferase / Q000378:metabolism*; D002118:Calcium / Q000502:physiology*; D002645:Chickens; D002940:Circadian Rhythm; D003035:Cobalt / Q000494:pharmacology; D003624:Darkness; D005711:Gallopamil / Q000494:pharmacology; D007473:Ion Channels / Q000502:physiology; D008274:Magnesium / Q000494:pharmacology; D008550:Melatonin / Q000502:physiology; D009543:Nifedipine / Q000494:pharmacology; D010870:Pineal Gland / Q000502:physiology; D051381:Rats; D012160:Retina / Q000201:enzymology* / Q000378:metabolism; D014268:Trifluoperazine / Q000494:pharmacology; D014982:Xenopus laevis
D007473:Ion Channels; D014268:Trifluoperazine; D005711:Gallopamil; D003035:Cobalt; D000123:Acetyltransferases; D001191:Arylamine N-Acetyltransferase; D008274:Magnesium; D009543:Nifedipine; D008550:Melatonin; D002118:Calcium