Abstract
Summary
1. A study has been made of the level of phosphoprotein phosphatase activity in placentas, whole embryos, and whole young growing rats of various ages.
2. The total phosphoprotein phosphatase activity of the placenta and of the embryo and young rats continually rises. The activity was followed in placenta and embryo from thirteen days post-conception to parturition, and in young rats to 28 days of age.
3. The activity per gram of body weight rises slowly in early embryos, rapidly in the period immediately preceding and following parturition, and remains essentially constant during the age period of 12 to 28 days.
4. The activity per gram of placenta decreases from the 14th to the 20th day after conception, then rises again just before parturition. The preliminary decrease is due to the rate of weight gain of the placenta being greater than the rate of gain of total placenta phosphoprotein phosphatase; the reversal of direction of the curve is due to continued enzyme increase while the placenta gains essentially no further weight.
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