LIGHT-EVOKED DISK SHEDDING BY ROD PHOTORECEPTORS INVITRO - RELATIONSHIP TO MEDIUM BICARBONATE CONCENTRATION

  • 1 January 1980
    • journal article
    • research article
    • Vol. 19  (12) , 1512-1517
Abstract
The control of photoperiod-related shedding by rod photoreceptors in frogs [Xenopus laevis] implies the mechanisms which initiate shedding are intrinsic features of the eye. Attempts to observe light-evoked shedding in opened eye cups in balanced salt solutions were unsuccessful. Disc shedding was examined in eye cups kept in a complex tissue culture medium. Eye cups were prepared in red light from dark-adapted animals or in white light from constant light-treated animals. Light-evoked shedding did not occur in the standard medium with .apprx. 20 mM NaHCO3, but a large light-evoked response was consistently seen when medium HCO3- was raised to .apprx. 30 mM. In high-HCO3- medium, light-evoked shedding was comparable in magnitude, size distribution of phagosomes and time course to similar responses observed in intact animals. In culture conditions which support shedding, HCO3- concentration seemed to be of critical importance. Lack of light-evoked shedding in a high-bicarbonate Ringer solution implied that some additional unidentified factor(s) in the complex medium was necessary. Light- and dark-dependent processes involved in the control of photoperiod-related shedding apparently are sustained in appropriate culture medium.