Alteration of ringer pH and its effects on precursor incorporation into Drosophila salivary gland nuclei

Drosophila salivary glands were explanted and incubated with ³H-uridine (or ³H-thymidine) in Ringer's solution (Ephrussi-Beadle modified saline) adjusted to pH values in the integral range, 4 to 10. The results of autoradiographic investigations indicate a differential effect of altering Ringer pH on ³H-uridine as opposed to ³H-thymidine incorporation: a) Relatively uniform levels of chromosomal incorporation of ³H-thymidine occurred over the range of test pH. Some decrease of incorporation was noted at pH 5 and some increase at pH 9. b) Chromosomal incorporation of ³H-uridine was severely depressed at pH 4 and 7 relative to the high incorporation levels observed at other pH values. Controlling pH of Ephrussi-Beadle Ringer's solution in such experiments seems a necessity. This appears especially important for studies involving ³H-uridine incorporation.