Morita T, Watanabe Y, Takeda K, Okumura K
Tokyo Research Laboratories, Nippon Glaxo Ltd., Japan.
Mutat Res. 1989 Jan-Feb;225(1-2):55-60. doi: 10.1016/0165-7992(89)90033-x.
The relation between the pH of the medium and clastogenic activity was studied in Chinese hamster ovary (CHO) K1 cells in vitro. The pH was adjusted with NaOH, KOH, HCl or H2SO4. No clastogenic activity was observed over the initial pH range of 7.3-10.9 without S9 mix, but a few chromosomal aberrations were induced at pH 10.4 with S9 mix. The frequency of aberrations increased with the increase in amount of S9. At acidic pH, many chromatid breaks were induced at initiatial pH 5.5 or below without S9 mix, and aberrations such as chromatid breaks and chromatid exchanges were induced at initial pH 6.2 or below with S9 mix. Using MES and Bis-Tris as buffers instead of sodium bicarbonate, we observed that aberrations of the chromatid break type were inducible at pH 6.2 or below. These results show that the combination of strong alkalinity and S9 is clastogenic to CHO-K1 cells, and also that weakly acidic media are genetically active. The results indicate that incubations at non-physiological pH might give false-positive responses.
在中国仓鼠卵巢（CHO）K1细胞中体外研究了培养基pH值与致断裂活性之间的关系。用氢氧化钠、氢氧化钾、盐酸或硫酸调节pH值。在无S9混合物的初始pH值7.3 - 10.9范围内未观察到致断裂活性，但在pH 10.4有S9混合物时诱导出了一些染色体畸变。畸变频率随S9量的增加而增加。在酸性pH值下，在初始pH 5.5或更低且无S9混合物时诱导出许多染色单体断裂，在初始pH 6.2或更低且有S9混合物时诱导出染色单体断裂和染色单体交换等畸变。使用MES和Bis - Tris作为缓冲剂代替碳酸氢钠时，我们观察到在pH 6.2或更低时可诱导出染色单体断裂类型的畸变。这些结果表明，强碱性与S9的组合对CHO - K1细胞具有致断裂性，并且弱酸性培养基具有遗传活性。结果表明在非生理pH值下孵育可能会产生假阳性反应。
