Effect of irradiation on the proliferation kinetics of thyroid follicular cells in infant rats.
Changes in the 3H-thymidine labeling index (LI), cell cycle time (TC) and growth fraction (GF) of the thyroid follicular cells were studied in 10 days old rats irradiated in the neck region with a single dose of 3 Gy X-rays. During the first 2 days after irradiation the number of proliferating follicular cells sharply increased, followed between the 2nd and 6th days by a phase of sharp decrease. Later, between the 10th and 16th days again an increase in the LI was observed. During the cell proliferation phase, the cell cycle was shortened from 79 hours in the control animals to 30.9 hours in irradiated animals. The GF was decreased from 40% in the former to 25% in the latter. S-phase duration (TS) was 1.6 hours longer in irradiated animals than in controls. The shortening of the cell cycle of irradiated animals is predominantly a result of diminishing G1-phase duration.
D000818:Animals; D000831:Animals, Newborn; D001345:Autoradiography; D002453:Cell Cycle / Q000528:radiation effects; D008297:Male; D008938:Mitosis / Q000187:drug effects; D009333:Neck / Q000528:radiation effects*; D009929:Organ Size / Q000528:radiation effects; D051381:Rats; D011919:Rats, Inbred Strains; D013961:Thyroid Gland / Q000528:radiation effects*; D014965:X-Rays