Zonal expression of the glucokinase gene in rat liver. Dynamics during the daily feeding rhythm and starvation-refeeding cycle demonstrated by in situ hybridization.
The abundance and zonal distribution of glucokinase (GK) mRNA were studied in rat liver during a normal 12 h day/12 h night rhythm (dark from 1900 to 0700 hours) and during refeeding after 60 h of starvation. Zonation of GK gene expression was examined by in situ hybridization with a radiolabelled cRNA probe and GK mRNA abundance was determined by Northern blot analysis with a digoxigenin-labelled cRNA probe. GK mRNA appeared to be almost homogeneously distributed throughout the whole daily feeding cycle; yet it was predominantly localized in the perivenous and intermediate zone during refeeding after 60 h of starvation. During the daily feeding rhythm, the total amount of GK mRNA increased quickly with the beginning of the feeding period at 1900 hours reaching a maximum at midnight and then decreased continuously to a basal level at noon. Virtually no GK mRNA was detected after 60 h of starvation. Refeeding caused a rapid increase in GK mRNA to a maximum at 2400 hours followed by a decrease to approximately two-thirds of the maximum value at 0700 hours. If the homogeneous distribution of GK mRNA during the daily feeding rhythm was real rather than apparent because of too low a sensitivity of the cRNA probe, the present results suggest that during the normal circadian cycle the mainly perivenous distribution of GK enzyme activity and protein is regulated preferentially at a translational level. The findings clearly show that during refeeding after 60 h of starvation the GK distribution is controlled predominantly at a pretranslational level.
Eilers
F
F
Institut für Biochemie und Molekulare Zellbiologie, Georg-August Universität, Göttingen, Germany.
Bartels
H
H
Jungermann
K
K
D000818:Animals; D015152:Blotting, Northern; D002940:Circadian Rhythm / Q000502:physiology; D004435:Eating / Q000502:physiology*; D015971:Gene Expression Regulation, Enzymologic / Q000502:physiology*; D005941:Glucokinase / Q000096:biosynthesis* / Q000235:genetics; D006651:Histocytochemistry; D017403:In Situ Hybridization; D008099:Liver / Q000201:enzymology*; D008297:Male; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D013217:Starvation / Q000378:metabolism*
D012333:RNA, Messenger; D005941:Glucokinase