Gestational variation of glycerophosphate acyltransferase activity in maternal guinea pig lung and possible role of thyroid hormone in its de novo synthesis.
We have observed earlier that the pattern of gestational variation of microsomal glycerophosphate acyltransferase (GAT) activity is similar in maternal and fetal guinea pig lung. Furthermore, there is a close resemblance between these patterns and that of the gestational variation of fetal plasma thyroid hormone. It is known that triiodothyronine (T3) injected to pregnant rats can cross the placenta to some extent and cause an increase in phosphatidylcholine synthesis in fetal lung. It is possible, therefore, that the gestational increase of GAT activity in maternal and fetal lung is associated with an increase in maternal plasma thyroid hormone. The objective of this study was to investigate whether intramuscular injection of T3 to adult guinea pig causes any change in the activity of GAT in lung and, if so, to determine the mechanistic basis. The results indicated that T3 significantly increased the GAT activity in the microsomes but not in the mitochondria. Actinomycin D or cycloheximide abolished the hormone-mediated stimulation of the enzyme in the microsomes, suggesting that T3 is involved in both transcriptional and translational pathways of GAT synthesis. We also confirmed our previous preliminary finding that there is a gestational variation of GAT activity in maternal guinea pig lung and furthermore the increase in GAT activity during pregnancy is predominantly in the microsomes.
Mukherjee
S
S
Department of Biochemistry, Meharry Medical College, Nashville, Tennessee 37208.
Nag
S
S
Das
S K
SK
D000818:Animals; D003513:Cycloheximide / Q000494:pharmacology; D003609:Dactinomycin / Q000494:pharmacology; D005260:Female; D005992:Glycerol-3-Phosphate O-Acyltransferase / Q000096:biosynthesis / Q000378:metabolism*; D006168:Guinea Pigs; D008168:Lung / Q000201:enzymology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000378:metabolism*; D014284:Triiodothyronine / Q000502:physiology*
D014284:Triiodothyronine; D003609:Dactinomycin; D003513:Cycloheximide; D005992:Glycerol-3-Phosphate O-Acyltransferase