THE INITIATION OF PROTEIN SYNTHESIS IN EGGS OF RANA PIPIENS

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Abstract
In the frog, Rana pipiens, the maturation of fully grown oocytes is initiated by pituitary hormones. The events of maturation include the breakdown of the germinal vesicle and the meiotic divisions up to the 2nd meiotic metaphase. After these events have taken place the eggs can be fertilized or artificially activated. Protein synthesis has been measured in eggs not only prior to injection of the pituitary suspension, but also afterwards, i.e., during the course of maturation through and including fertilization or artificial activation. The results of these experiments show that full-grown oocytes from unstimulated frogs are capable of a low but discrete level of protein synthesis. Synthesis increases only after the injection of donor frogs with a pituitary suspension. Thus, pituitary hormones appear to initiate protein synthesis in Rana pipiens eggs. Coincidental with the initiation of protein sysnthesls, the injection of pituitary also initiates breakdown of the germinal vesicle followed by the meiotic divisions. Whether or not there is a causal relationship between the morphological events of maturation and the increase in protein synthesis is uncertain. However, fertilization or artificial activation apparently have no immediate, quantitative effect on protein synthesis. These events appear to be merely superimposed upon the gross pattern of protein synthesis that was initiated many hr. earlier.