Cardiovascular tissues contain independent circadian clocks.
Acute cardiovascular events exhibit a circadian rhythm in the frequency of occurrence. The mechanisms underlying these phenomena are not yet fully understood, but they may be due to rhythmicity inherent in the cardiovascular system. We have begun to characterize rhythmicity of the clock gene mPer1 in the rat cardiovascular system. Luciferase activity driven by the mPer1 gene promoter is rhythmic in vitro in heart tissue explants and a wide variety of veins and arteries cultured from the transgenic Per1-luc rat. The tissues showed between 3 and 12 circadian cycles of gene expression in vitro before damping. Whereas peak per1-driven bioluminescence consistently occurred during the late night in the heart and all arteries sampled, the phases of the rhythms in veins varied significantly by anatomical location. Varying the time of the culture procedure relative to the donor animal's light:dark cycle revealed that, unlike some other rat tissues such as liver, the phases of in vitro rhythms of arteries, veins, and heart explants were affected by culture time. However, phase relationships among tissues were consistent across culture times; this suggests diversity in circadian regulation among components of the cardiovascular system.
Davidson
A J
AJ
Department of Biology, University of Virginia, Charlottesville, Virginia 22904-4328, USA ad2h@virginia.edu
London
B
B
Block
G D
GD
Menaker
M
M
D000818:Animals; D030801:Animals, Genetically Modified; D001158:Arteries / Q000166:cytology / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D056926:CLOCK Proteins; D002319:Cardiovascular System / Q000166:cytology / Q000378:metabolism*; D018797:Cell Cycle Proteins; D002940:Circadian Rhythm / Q000502:physiology*; D005260:Female; D015870:Gene Expression / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism; D009206:Myocardium / Q000166:cytology / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D056950:Period Circadian Proteins; D051381:Rats; D046509:Tissue Culture Techniques; D015534:Trans-Activators / Q000378:metabolism*; D014680:Veins / Q000166:cytology / Q000378:metabolism
D015415:Biomarkers; D018797:Cell Cycle Proteins; D009687:Nuclear Proteins; C539022:PER1 protein, human; C539024:Per1 protein, rat; D056950:Period Circadian Proteins; D015534:Trans-Activators; D056926:CLOCK Proteins; C538943:CLOCK protein, human; C538945:Clock protein, rat