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The effect of hypercapnia on cat brain gangliosides

IN AN earlier study (LOWDEN & WOLFE, 1964) we extracted gangliosides from cat brain with tetrahydrofuran. We found that when cats had been asphyxiated or ventilated with gas mixtures containing large amounts of carbon dioxide, the N-acetylneuraminic acid (NeuNAc) content of the mixture of extracted gangliosides was lower than that in gangliosides from normal brains. Subsequently HOLM (1968) examined cerebral gangliosides from rats that had been placed in a chamber flushed with 20% CO,, 20% 0, and 60% N,. He, extracted the brains with chloroform/methanol/2 N KOH and partitioned the gangliosides on silica gel columns. He found that the brains of hypercapnic rats contained the same amounts of glycolipid-NeuNAc as normal brains but he did not weigh and calculate the NeuNAc content of the mixture of extracted gangliosides. He did show, however, that the distribution of major ganglioside species in hypercapnic brain was not different from that in normal brain. We have therefore repeated our study with cats, extracting the brains with chloroform-methanol (SUZUKI, 1965). We have also examined the incorporation of [ 14C]glucosamine into cerebral gangliosides in normal brain. We do not find the changes we noted in tetrahydrofuran-extracted gangliosides and now believe our earlier results were based on pH-induced differences in extractability. However it is quite clear from the present study that hypercapnia decreases the incorporation of ['4C]glucosamine into polysialogangliosides.