Regulation of histidase gene expression by glucagon, hydrocortisone and protein-free/high carbohydrate diet in the rat.
The effect of glucagon and hydrocortisone was investigated to understand the mechanism of induction of hepatic histidase gene. In this study, glucagon (0.6 mg/100 g body wt/d) was injected to rats fed 10% casein diet. After 3 h of the last injection, histidase activity and amount of enzyme were induced by 3 fold and histidase mRNA concentration by 6 fold. Injection of hydrocortisone (2 mg/100 g body wt/d) increased 100% histidase activity and mRNA concentration and by 150% the amount of enzyme after 3 h of the last injection. These results indicate that glucagon is a better inductor of histidase gene expression than hydrocortisone. Another purpose of the study was to evaluate if a protein-free/high carbohydrate diet could reverse the induction of Hal expression produced by a high protein diet. Hal activity, amount of enzyme and mRNA concentration was repressed by 68, 88 and 95% respectively by a protein-free/high carbohydrate diet. Injection of glucagon reversed partially the effect of a high carbohydrate diet, however, injection of hydrocortisone under the concentration used in these experiments did not reverse the effect of a high carbohydrate diet. These results support the evidence that hepatic histidase gene expression is probably regulated transcriptionally by hormones.
Alemán
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G
Departamento de Fisiología de la Nutrición, Instituto Nacional de la Nutrición Salvador Zubirán, México, DF.
Torres
N
N
Bourges
H
H
Tovar
A R
AR
D000818:Animals; D015152:Blotting, Northern; D015153:Blotting, Western; D001835:Body Weight / Q000187:drug effects; D004032:Diet; D004040:Dietary Carbohydrates / Q000494:pharmacology*; D005765:Gastrointestinal Agents / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005934:Glucagon / Q000494:pharmacology; D006638:Histidine Ammonia-Lyase / Q000096:biosynthesis* / Q000235:genetics; D006854:Hydrocortisone / Q000494:pharmacology*; D008297:Male; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar
D004040:Dietary Carbohydrates; D005765:Gastrointestinal Agents; D012333:RNA, Messenger; D005934:Glucagon; D006638:Histidine Ammonia-Lyase; D006854:Hydrocortisone