Effect of aging on regulation of sdi-1 in rat hepatocytes.
We examined basal and EGF stimulated DNA synthesis as well as sdi-1 mRNA and protein in primary hepatocyte cultures, and basal levels of sdi-1 mRNA and protein in whole liver homogenates from 6 and 24 month old rats. Since EGF stimulated DNA synthesis decreases with age, it was hypothesized that basal and EGF stimulated levels of sdi-1 mRNA and protein, an inhibitor of DNA synthesis, might increase. Surprisingly, however both sdi-1 mRNA and protein actually decreased both in cells and homogenates of old rats. These results indicate that the age-related impairment in EGF stimulated DNA synthesis in hepatocytes appears to occur prior to or parallel with sdi-1 expression and cannot be explained on the basis of increased inhibition due to elevated levels of this protein.
Kitano
S
S
Molecular Physiology and Genetics Section, Gerontology Research Center, Baltimore, Maryland 21224, USA.
Venable
S
S
Smith
J R
JR
Reed
T D
TD
Roth
G S
GS
D000375:Aging / Q000378:metabolism*; D000704:Analysis of Variance; D000818:Animals; D015152:Blotting, Northern; D002478:Cells, Cultured; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000096:biosynthesis*; D004247:DNA / Q000096:biosynthesis; D004815:Epidermal Growth Factor / Q000494:pharmacology; D018507:Gene Expression Regulation, Developmental; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D008297:Male; D012333:RNA, Messenger / Q000032:analysis / Q000096:biosynthesis; D051381:Rats; D017208:Rats, Wistar; D013936:Thymidine / Q000378:metabolism; D014158:Transcription, Genetic / Q000187:drug effects
C493958:Cdkn1a protein, rat; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D012333:RNA, Messenger; D004815:Epidermal Growth Factor; D004247:DNA; D013936:Thymidine