RADIATION-INDUCED CHANGES IN THE KINETICS OF GLOMERULAR AND TUBULAR CELLS IN THE PIG-KIDNEY

Both kidneys of 13 mature female Large White pigs were irradiated with a single dose of 9.8 Gy Co-60 gamma rays. The pigs were killed serial ly between 2 to 24 weeks after irradiation. One hour prior to sacrific e bromodeoxyuridine (BrdU) (500 mg/pig) was injected intravenously. At postmortem the kidneys were removed and tissue was taken to prepare c ell suspensions. The labeling index (LI) of these suspensions was dete rmined using flow cytometry. In vivo BrdU incorporation in tubular and glomerular cells was determined immunohistochemically. The kinetics o f glomerular and tubular cells was evaluated by counting the number of labeled cells/glomerulus and the number of labeled tubular cells/fiel d of view. An average of 1200 glomeruli and 1500 fields of view/time w ere counted. Similar analyses were performed on renal tissue from unir radiated control animals. Flow cytometry revealed rapid and significan t increases in the LI of kidney cells; 2 weeks after irradiation the L I increased from a control value of 0.18 +/- 0.01 to 1.23 +/- 0.22% (P < 0.001). By 4 weeks the maximal value of 2.45 +/- 0.36% was seen; th e LI then declined progressively but at 24 weeks after irradiation sti ll remained significantly above control values (P < 0.001). A similar pattern of response was determined by counting the labeled glomerular and tubular cells identified immunohistochemically. However, the incre ase in labeled glomerular cells occurred 2 weeks after irradiation, wh ereas that for the tubules occurred 4 weeks after irradiation. These f indings indicate that irradiation of the kidney, classically regarded as a ''late-responding'' organ, is associated with rapid and significa nt changes in the kinetics of both tubular and glomerular cells.