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KMID : 0351619710120010037
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Kyungpook Medical Journal
1971 Volume.12 No. 1 p.37 ~ p.49
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The Influence of Circadian Rhythm in the Cell Cycle Studies with 3H-thymidine Autography
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Abstract
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In recent years knowledge about kinetics of various cell systems was considerably increa:,ed -by application of the autoradiographic method, especially through the use of 3H-thymidine as a label of cells in DNA synthesis. Cell cycle times of intermitotic cells have been estimated for a variety of animal and some human tissues.
In such kinetic studies, the individual variations of single cells being lost in the mean valcie.
During cell cycle study in our laboratory, however, significant variations have been concerned with 24 hour cycles, but the difference of their cycle times have not yet been cleared up for intact tissues in the mammalians.
The purpose of the present investigation was firstly to find out if there are a diurnal variations in the number of DNA-synthesizing cells, such as hepatic cells, cardiac muscle cell and cryptal cells of small intestine. Secondary to see if thE;re are any correlation between the proliferation r:~te of the different cell population and the diurnalvariations.
Several results were obtained as followings:
1. In the liver cells of 17th day of gestation, and 20 day postnatal mice showed significant circadian rhythm, which was distinguished in G~ phase and ascending slopes of 2nd cell cycle, and not in S phase.
2. In the cryptal cell population of small intestine, no influence of circadian rhythm was recognized at any experimental groups.
3. The cardiac muscle cell population in both 17th day of gestation and 20th day postnatal mouse showed circadian variations significantly which were prolonged S phase, and total generation times.
It can be concluded that only those cell population which proliferate at a slow speed and which have a low DNA synthetic index (below 10~) should be considered circadian rhythm in the autoradiographic studies.
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