Synthesis of soluble protein in oocytes of Xenopus laevis

Oocytes of five stages of development were isolated from ovaries of Xenopus laevis and allowed to take up radioactive amino acids. After six hours of labeling the amount of label incorporated into perchloric acid precipitable material from the soluble oocyte fraction and the specific activity of the label free pool was determined. From these figures an estimate of the rate of protein synthesis was calculated. Labeled soluble protein from each oocyte stage was analyzed by electrophoresis on SDS polyacrylamide gels. The gel was dried and autoradiographed to determine the qualitative pattern of soluble protein synthesis during various stages of oogenesis. Our results indicate that no significant differences exist in the rate of protein synthesis among any of the stages of oogenesis investigated. The qualitative pattern of soluble protein synthesized during the labeling period is similar among the oocyte stages. Moreover, this qualitative pattern of soluble protein synthesis is the same as the pattern of soluble protein accumulated up to that time during oogenesis. These results suggest a stable synthesis and accumulation of maternal protein products during Xenopus oogenesis, in marked contrast to the results that have been reported for RNA synthesis during oogenesis in Xenopus. Our results are discussed in terms of the present understanding of the process of maternal information accumulation.