The hierarchy of requirements for an elevated intracellular pH during early development of sea urchin embryos

Abstract

The intracellular pH (pH l) rises 0.3–0.5 units after fertilization of sea urchin eggs, and this and previous work show this pH l change is necessary for initiating the developmental processes leading to cell division. The experiments described here reveal that while the elevated pHi is permanently required for a normal early development, lowering pH l of embryos after fertilization affects different processes to different extents. Protein synthesis gradually becomes less sensitive to pH l. Karyokinesis proceeds to completion under a low pH l, but is retarded, while cytokinesis is always impaired. These results indicate a hierarchy of requirements for high pHi during early development of sea urchin embryos, with protein synthesis, karyokinesis, and cytokinesis showing, respectively, increasing requirements for an elevated pH l.