Species differences in the response of mammalian photoreceptor cyclic GMP and PIII to a reduction in calcium.
Changes in the content of cyclic GMP (cGMP), induced by exposure of isolated, dark-adapted mouse, cat and dog retinas to media depleted of calcium, have been compared with the amplitude of the trans-retinal PIII. Major differences exist in the time-course and magnitude of effects between the species and, in the cat and dog, changes in PIII (potentially a reflection of free cGMP in photoreceptor outer segments) do not correlate with those occurring in total cGMP. The observations imply species variation, not only in the enzymes maintaining cGMP homeostasis in photoreceptors, but also in phototransduction and allied processes.
Hussain
A A
AA
Department of Visual Science, Institute of Ophthalmology, University of London, England.
Willmott
N J
NJ
Voaden
M J
MJ
D000818:Animals; D002118:Calcium / Q000494:pharmacology*; D002415:Cats; D006152:Cyclic GMP / Q000378:metabolism*; D003623:Dark Adaptation / Q000502:physiology; D004285:Dogs; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D008810:Mice, Inbred C57BL; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000378:metabolism* / Q000502:physiology; D013997:Time Factors
D006152:Cyclic GMP; D002118:Calcium