Hormonal induction of malic enzyme in rat hepatocytes cultured on laminin-rich gels.
The levels of malic-enzyme mRNA and activity were determined in primary cultures of adult rat hepatocytes maintained on either rat-tail collagen or a laminin-rich substratum. Cells plated on laminin-rich gels exhibited substantially improved patterns of albumin and malic-enzyme expression when compared with cells maintained on rat-tail collagen. Moreover, hepatocytes plated on the laminin-rich matrix displayed marked malic-enzyme inducibility in response to tri-iodothyronine and dichloroacetate, especially in the presence of insulin. However, Northern blot analysis revealed that the ratio of the amounts of the two major malic-enzyme mRNA species (2.0 and 3.1 kb) was reversed when compared with that found in the liver in vivo, the altered levels of these two species being closer to those found in non-hepatic tissues. These findings indicate that, although the hormonal responsiveness of isolated hepatocytes maintained on laminin-rich gels is markedly improved, and approaches the degree of induction demonstrated in the liver in vivo, the mechanisms of control differ, indicating a loss of liver-specific expression.
Mann
D J
DJ
Department of Molecular Biology and Biotechnology, University of Sheffield, U.K.
Strain
A J
AJ
Bailey
E
E
D000818:Animals; D002478:Cells, Cultured; D003094:Collagen; D003999:Dichloroacetic Acid / Q000494:pharmacology; D004790:Enzyme Induction; D015971:Gene Expression Regulation, Enzymologic; D006728:Hormones / Q000502:physiology*; D007328:Insulin / Q000502:physiology; D008099:Liver / Q000166:cytology / Q000201:enzymology*; D008291:Malate Dehydrogenase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism; D008297:Male; D012333:RNA, Messenger / Q000378:metabolism; D051381:Rats; D014284:Triiodothyronine / Q000502:physiology
D006728:Hormones; D007328:Insulin; D012333:RNA, Messenger; D014284:Triiodothyronine; D003094:Collagen; D003999:Dichloroacetic Acid; D008291:Malate Dehydrogenase