The role of cyclic AMP in the control of elasmobranch ocular tapetum lucidum pigment granule migration.
We have studied the effect of adding cAMP to dogfish ocular tapetum lucidum tissue maintained in vitro. Normally, under conditions of dark-adaptation, tapetal pigment granules attain an aggregated state, exposing highly reflective cellular plates (which contain crystalline guanine) to incident illumination. The reflected light from these plates is believed to function in the visual process by increasing photoreceptor photon capture under low light conditions. Upon illumination, the pigment granules attain a dispersed state, occluding the reflective surfaces. We found that this occlusion may be mimicked in dark-adapted tissue in vitro by adding cAMP, or by the use of agents believed to increase intracellular cAMP concentrations such as forskolin and IBMX. Additionally, aggregation of pigment in light-adapted tissue transferred to darkness is inhibited by such agents. The results of this and previously published studies indicate that the processes of pigment aggregation and dispersal in vivo are under the control of the neural retina through the probable mediation of either hormonal or direct neural communication.
Heath
A R
AR
Department of Biomedical Sciences, Pennsylvania College of Optometry, Philadelphia 19141.
Hindman
H M
HM
D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002829:Choroid / Q000187:drug effects*; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000494:pharmacology*; D003594:Cytoplasmic Granules / Q000187:drug effects; D003623:Dark Adaptation; D004284:Dogfish / Q000502:physiology*; D008297:Male; D010860:Pigments, Biological; D012754:Sharks / Q000502:physiology*
D010860:Pigments, Biological; D005576:Colforsin; D003994:Bucladesine; D000242:Cyclic AMP; D015056:1-Methyl-3-isobutylxanthine