The effects of imbalanced subunit synthesis, temperature, colchicine, and cytochalasin on the secretion from Xenopus laevis oocytes of a variety of avian and mammalian proteins were investigated; these proteins were encoded by microinjected messenger RNA. Cytochalasin and colchicine together severely reduced secretion in a temperature-independent manner, the exact reduction varying among the different proteins. In contrast cytochalasin alone had no effect, whereas colchicine alone caused a smaller, temperature-dependent reduction. The synthesis and subcellular compartmentation of these proteins were unaffected by the drug treatments; however, the proteins did not accumulate in the drug-treated oocytes but were degraded. The rate of degradation of each protein was similar to its rate of exocytosis from untreated oocytes. A similar result was obtained without recourse to drugs by studying the fate of immunoglobulin light chains trapped in oocytes by a deficiency in heavy chain synthesis. These results are discussed in terms of the disruptive effects, as revealed by electron microscopy, of the drug treatments on the cytoskeleton of the oocyte.

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