Maturation of the fetal lung III. Effect of transplacental TRH and 2'-thiourea treatment on phosphatidic acid phosphatase and pyruvate kinase activity in rat lung.

The activity of pyruvate kinase (PK), an enzyme playing a key role in glycolysis, was studied in the lung of Wistar R/A rats in the prenatal, postnatal and adult periods of life. The highest level was measured on the 20th gestational day, a value nearly double the adult mean. In order to elicit fetal hypothyroidism, pregnant rats were treated with 0.1% thiourea solution from the 14th day of gestation up to delivery. The animals were killed on the 21st or 22nd gestational day or on the 2nd postnatal day. A significant increase in PK activity was seen in the treated animals as compared to the control group, while the activity of phosphatidic acid phosphatase (PAPase) remained unchanged. Fetal hyperthyroidism was induced by intravenous injections of TRH to the pregnant mother rat. This resulted in an increase of PAPase and a decrease of PK activity as compared to the control group. The difference was statistically significant in all instances, the level of significance, however, depended on the time when treatment had been initiated.