Effect of vitamin A deficiency and retinoic acid repletion on intestinal and hepatic apolipoprotein A-I mRNA levels of adult rats.
Apolipoprotein A-I (apoA-I) gene expression is known to be regulated by nutritional and hormonal factors. Experiments were conducted to determine the effects of vitamin A deficiency and retinoic acid repletion on the in vivo expression of apoA-I in rat intestine and liver. The relative abundance of apoA-I mRNA (apoA-I/beta-actin ratio) in the intestine did not differ significantly between vitamin A-deficient and -sufficient rats. However, the relative abundance of hepatic apoA-I mRNA of vitamin A-deficient rats was 2.2- to 6-times that of sufficient rats. Even marginal vitamin A status resulted in a significant increase in hepatic apoA-I mRNA expression. Treatment of vitamin A-deficient rats with a single dose of retinoic acid (20 micrograms, 20 h before tissues were collected) reduced the hepatic apoA-I mRNA/beta-actin ratio by about 40%, while further reduction (about 60-65%) was observed after two treatments with retinoic acid. By nuclear run-on assay, the increase in hepatic apoA-I mRNA in vitamin A-deficient rats was attributable to increased transcription of the apoA-I gene. However, immunoblot analysis showed no apparent differences in apoA-I protein in either liver homogenates or plasma of vitamin A-deficient and -sufficient rats. These data indicate that apoA-I gene expression in vivo is sensitive to retinoid status and suggest that there is additional regulation of post-transcriptional events.
Zolfaghari
R
R
Department of Biochemistry, Medical College of Pennsylvania, Philadelphia 19129.
Ross
A C
AC
D000818:Animals; D016632:Apolipoprotein A-I / Q000235:genetics* / Q000378:metabolism; D015152:Blotting, Northern; D002467:Cell Nucleus / Q000378:metabolism; D015342:DNA Probes; D005260:Female; D007413:Intestinal Mucosa / Q000378:metabolism*; D008099:Liver / Q000378:metabolism* / Q000648:ultrastructure; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011917:Rats, Inbred Lew; D014158:Transcription, Genetic; D014212:Tretinoin / Q000008:administration & dosage* / Q000627:therapeutic use; D014802:Vitamin A Deficiency / Q000378:metabolism*
D016632:Apolipoprotein A-I; D015342:DNA Probes; D012333:RNA, Messenger; D014212:Tretinoin