Sofuni, T; Yamazaki, N; Matsuoka, A; Suzuki, T; Hayashi, M
OUR PREVIOUS STUDY ON CHROMOSOME ABERRATION INDUCTION IN THE CHL AND CHO CELL SYSTEMS INDICATED THAT 44% OF 25 TEST CHEMICALS HAD QUALITATIVELY INCONSISTENT RESULTS. TO ELUCIDATE FACTORS WHICH MAY INFLUENCE THE RESULTS, AN INTERNATIONAL COLLABORATIVE STUDY IS BEING CARRIED OUT BY 8 LABORATORIES IN THE U.S.A., THE U.K. AND JAPAN. THE PRESENT STUDY WAS PERFORMED AS A PART OF THIS COLLABORATIVE STUDY. FOUR CHEMICALS, N,N'-DIPHENYL-P-PHENYLENEDIAMINE (DPPD), N,N'-DI-2-NAPHTHYL-P-PHENYLENEDIAMINE (DNPD), TRIALLYL ISOCYANURATE (TAIC) AND 2,3,4- TRICHLOROPHENOL (TCP) SUPPLIED BY NTP WERE TESTED USING 2 CHINESE HAMSTER CELL LINES, CHL AND CHO-WBL, ACCORDING TO 2 DIFFERENT TEST PROTOCOLS, THE CHL (LONG TREATMENT TIME) AND CHO (SHORT TREATMENT TIME) SYSTEMS. WHEN THE TEST WAS CARRIED OUT ACCORDING TO THE CHL PROTOCOL, DPPD AND DNPD SHOWED POSITIVE RESULTS ON BOTH CHL AND CHO CELLS WITHOUT S9 MIX, WHILE BOTH TEST CHEMICALS INDUCED A WEAK OR NO RESPONSE IN THE CHO TEST PROTOCOL ON BOTH CELLS. TAIC AND TCP WERE ALSO POSITIVE IN THE CHL PROTOCOL ON BOTH CHL AND CHO CELLS WITH S9 MIX, BUT INDUCED A WEAK OR NO RESPONSE IN THE CHO PROTOCOL ON BOTH CELLS. USING THE BUDR-LABELING METHOD, IT WAS FOUND THAT ABOUT 50% OF CHL CELLS OF THE SOLVENT CONTROL WERE IN THE SECOND CELL DIVISION AT THE 24-H HARVEST TIME, WHILE ALMOST ALL CELLS TREATED WITH THE HIGHEST DOSE OF DPPD AND DNPD WERE IN THE FIRST CELL DIVISION. AT A 48-H HARVEST TIME 40-60% OF THE SOLVENT CONTROL CELLS WERE IN THE THIRD DIVISION, AND ABOUT 80% AND 50% OF CELLS WERE IN THE SECOND DIVISION AFTER TREATMENT WITH THE HIGHER DOSES OF DPPD AND DNPD, RESPECTIVELY. A SIMILAR TENDENCY WAS ALSO OBSERVED IN CHO CELLS. THE PRESENT RESULTS INDICATE THAT TO OBTAIN RELIABLE TEST RESULTS THE EXPERIMENTAL PROTOCOL IS MORE IMPORTANT THAN THE CHARACTERISTICS OF THE CELLS USED. FURTHER, IT IS EVIDENT THAT A MARKED CELL-CYCLE DELAY WAS CAUSED BY TREATMENT WITH HIGH DOSES OF TEST CHEMICALS, SUPPORTING THE NOTION THAT THE LONG TREATMENT PROTOCOL IS MORE EFFECTIVE FOR DETECTING CHROMOSOME ABERRATIONS IN CULTURED CELLS.
