A phase-dependent delay of the chick pineal rhythm in rate of thymidine incorporation by brief exposure to ouabain.
Cultured chick pineal glands show a persistent rhythm in the rate of cumulative incorporation of thymidine into DNA [Wainwright and Wainwright, 1989]. In this study we have examined the effects of a pulse-exposure to ouabain in the dark on the first day of culture upon thymidine incorporation during the second and third days of culture in the dark with ouabain-free medium. The phase of the rhythm in rate of thymidine incorporation was delayed by a 4-hr exposure to 100 microM ouabain commencing in the final hour of the photoperiod, but not by a 2-hr exposure or by 10 microM ouabain. This effect was phase-dependent and not seen when exposure to ouabain began earlier in the photoperiod. The phase delay caused by ouabain was not due to a persistent direct inhibition of the process of thymidine incorporation. The phase-shift due to exposure to ouabain was superimposed on a phase delay caused by renewal of culture medium 4 hr after explanting the glands into culture.
Wainwright
S D
SD
Biochemistry Department, Dalhousie University, Halifax, Nova Scotia, Canada.
Wainwright
L K
LK
D000818:Animals; D001683:Biological Clocks / Q000187:drug effects*; D002645:Chickens / Q000378:metabolism*; D004261:DNA Replication / Q000187:drug effects / Q000502:physiology*; D009924:Organ Culture Techniques; D010042:Ouabain / Q000494:pharmacology*; D017440:Photoperiod; D010870:Pineal Gland / Q000187:drug effects / Q000378:metabolism*; D013936:Thymidine / Q000378:metabolism
D010042:Ouabain; D013936:Thymidine