On the determination of the dorso-ventral polarity in the amphibian embryo: suppression by lactate of the formation of Ruffini's flask-cells.

Cells isolated from the vegetal hemisphere of the blastula of Ambystoma mexicanum differentiate spontaneously into fibroblast-like cells. Similar cells may be formed from animal cells, provided they are induced either by vegetal cells or by Li+. We have found that lactate and various inhibitors of RNA synthesis suppress the spontaneous cell differentiation. The effect of lactate differs from that of the other agents in so far as lactate must be present before the second day of culture to suppress the outgrowth of fibroblasts on the third day; the other inhibitors are active also when added on the second day. An explanation of this difference may possibly be found in the fact that lactate suppresses incorporation of RNA but only by 40%. The effect on the differentiation of various substances supposed to interfere with the metabolism of lactate was established. The results obtained were suggestive, but not conclusive. It is concluded that the effect of anaerobiosis may be explained as a lactate inhibition. The amounts of lactate under aerobic conditions are so slight that it is unlikely, but not impossible, that lactate is directly involved in the control of differentiation.