title: Studies on the biogenesis of smooth endoplasmic reticulum membranes in hepatocytes of phenobarbital-treated rats. II. The site of phospholipid synthesis in the initial phase of membrane proliferation.
abstract: The specific activity of the acyltransferases of smooth microsomes of rat liver rose threefold by 12 h after injection of phenobarbital, while the activity of the acyltransferases of the rough microsomes rose slightly to peak at 3-4 h, and subsequently fell. The latter rise was abolished by treatment of the animal with actinomycin D or puromycin, while that of the smooth microsomes was unaffected. Incorporation of [(14)C]glycerol into phospholipid of smooth microsomes was elevated 100% by phenobarbital, while that of the rough microsomes was elevated 15%, and this could be accounted for by exchange between the microsomal phospholipids. The phospholipid/protein ratio of the smooth microsomes rose 1.5 times 3-4 h after injection of phenobarbital, while that of the rough microsomes fell slightly. The specific activity of NADPH cytochrome c reductase and NADPH diaphorase rose first in the rough microsomes, and subsequently in the smooth microsomes at a time coinciding with the return of the phospholipid/protein ratio to the control level. The rise in phospholipid/protein ratio was unaffected by actinomycin D or puromycin. These results indicate that the proliferating smooth membranes are the site of phospholipid synthesis, and that the phospholipid/protein ratio of these membranes may change independently.
mesh_terms: D000217:Acyltransferases / Q000378:metabolism; D000818:Animals; D002250:Carbon Radioisotopes; D002455:Cell Division; D003579:Cytochrome Reductases / Q000378:metabolism; D003609:Dactinomycin / Q000494:pharmacology; D008058:Dihydrolipoamide Dehydrogenase / Q000378:metabolism; D004721:Endoplasmic Reticulum / Q000378:metabolism*; D005990:Glycerol / Q000378:metabolism; D008099:Liver / Q000166:cytology*; D008297:Male; D008566:Membranes / Q000378:metabolism*; D008862:Microsomes, Liver / Q000201:enzymology*; D009249:NADP; D010634:Phenobarbital / Q000494:pharmacology*; D010743:Phospholipids / Q000096:biosynthesis*; D011506:Proteins / Q000378:metabolism; D011691:Puromycin / Q000494:pharmacology; D051381:Rats; D013997:Time Factors
chemical_list: D002250:Carbon Radioisotopes; D010743:Phospholipids; D011506:Proteins; D003609:Dactinomycin; D011691:Puromycin; D009249:NADP; D003579:Cytochrome Reductases; D008058:Dihydrolipoamide Dehydrogenase; D000217:Acyltransferases; D005990:Glycerol; D010634:Phenobarbital