Dose-related effect of irradiation on circadian rhythm of cellular messengers in neural and immune system of mouse.
OBJECTIVE
To explore toxic effect of gamma-irradiation on circadian rhythms of cAMP and cGMP in signal pathway between the central nuclei and peripheral lymphocyte.


METHODS
60Co gamma-ray of 0.5 Gy and 5.0 Gy was applied to groups of mice at each circadian timepoint of a day. 24 hours after the irradiation, the pineal and suprachiasmatic nuclei (SCN) were removed, and the T lymphocytes in blood were separated by a step-centrifugal and nylon-filter treatment, for measurements of cAMP and cGMP by using the RIA procedure. The results were expressed as circadian rhythms of the cAMP/cGMP ratio derived from the Cosinor analysis.


RESULTS
The daily average cAMP/cGMP ratio in cells of SCN, pineal, serum and lymphocyte changed according to the dose of irradiation at which the mice were exposed. The high dose of 5 Gy increased the ratio, and the low dose of 0.5 Gy decreased the ratio. There was a significant difference of cAMP/cGMP levels between the irradiated and the control groups, as well as between CT00:00 and CT12:00 of a day. In addition, the peak phases of the cAMP/cGMP ratio at the low-dose groups appeared in advance from about 2 to 8 hours, whereas those at the high-dose groups were delayed from about 3 to 6 hours in comparison to that of the normal mice.


CONCLUSIONS
Toxic effect of gamma-irradiation on the cAMP/cGMP circadian rhythm in the central nuclei and peripheral lymphocyte could be characterized by a low-dose hormesis.
Tong
J
J
Department of Radiation Medicine, Suzhou Medical College, Suzhou 215007, China.
Qin
L
L
Geng
M
M
D000818:Animals; D002940:Circadian Rhythm / Q000528:radiation effects*; D003037:Cobalt Radioisotopes / Q000009:adverse effects; D000242:Cyclic AMP / Q000378:metabolism / Q000528:radiation effects*; D006152:Cyclic GMP / Q000378:metabolism / Q000528:radiation effects*; D004307:Dose-Response Relationship, Radiation; D005720:Gamma Rays / Q000009:adverse effects*; D008214:Lymphocytes / Q000276:immunology / Q000528:radiation effects; D008297:Male; D051379:Mice; D010870:Pineal Gland / Q000502:physiology / Q000528:radiation effects*; D011829:Radiation Dosage; D015398:Signal Transduction
D003037:Cobalt Radioisotopes; D000242:Cyclic AMP; D006152:Cyclic GMP