title: Guanylate cyclase in rod outer segments of the toad retina. Effect of light and Ca2+.
abstract: Guanylate cyclase activity was measured in disrupted rod outer segments of the toad retina. The experiments showed that cGMP is synthesized from GTP at a rate of 3 +/- 1 nmol/min per mg protein. In darkness this value is largely independent of the Ca2+ concentration, while it is enhanced by flashes of light of increasing intensity upon lowering Ca from 10-5 to 10-8 M. In view of recent observations that shortly after a flash of light calcium activity inside the photoreceptor cell decreases, it seems likely that calcium plays a regulatory role in cGMP metabolism in visual excitation.
authors.forename: I M
authors.initials: IM
authors.lastname: Pepe
authors.forename: I
authors.initials: I
authors.lastname: Panfoli
authors.forename: C
authors.initials: C
authors.lastname: Cugnoli
mesh_terms: D000818:Animals; D002023:Bufo bufo; D002118:Calcium / Q000494:pharmacology; D006152:Cyclic GMP / Q000378:metabolism; D006162:Guanylate Cyclase / Q000378:metabolism*; D066298:In Vitro Techniques; D008027:Light; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D010786:Photoreceptor Cells / Q000201:enzymology*; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000201:enzymology* / Q000528:radiation effects
chemical_list: D010727:Phosphoric Diester Hydrolases; D006162:Guanylate Cyclase; D006152:Cyclic GMP; D002118:Calcium