Hepatic carnitine palmitoyltransferase turnover and translation rates in fed, starved, streptozotocin-diabetic and diethylhexyl phthalate-treated rats.
Hepatic carnitine palmitoyltransferase (CPT) turnover was studied in control and in non-ketotic hyperglycaemic streptozotocin-diabetic rats. The degradation constant (kd) and half-life (t1/2) did not appear to be altered by mild diabetes. The hepatic CPT (micrograms/g of liver) was not increased by the mild, non-ketotic, diabetes. However, the total hepatic CPT (micrograms/liver) was 37% greater in the diabetic animals, owing to the increased liver weight. This resulted from a 40% increase in the synthesis constant (ks). Hepatic CPT activity (total detergent-solubilized) and translation rates were measured in fed, starved (48 h), non-ketotic diabetic, ketotic diabetic and diethylhexyl phthalate (DEHP)-treated rats. CPT activity (m units/mg of mitochondrial protein) was not significantly increased with non-ketotic diabetes (44% increase, but non-significant), but was increased approx. 2-fold with starvation and ketotic diabetes, and 3.5-fold with DEHP treatment. CPT expressed as units/liver was increased non-significantly (23%) in non-ketotic and starved rats, similar to the turnover study, but was significantly increased with ketotic diabetes and with DEHP treatment. mRNA-translation activity for CPT was elevated in all states to a somewhat greater extent than was activity. It was concluded that protein synthesis as a product of increased CPT-mRNA translation activity is a major means of long-term regulation.
Department of Food Science and Human Nutrition, Washington State University, Pullman 99164-2032.
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D000217:Acyltransferases / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000032:analysis; D002334:Carnitine O-Palmitoyltransferase / Q000235:genetics / Q000276:immunology / Q000378:metabolism*; D003902:Detergents / Q000494:pharmacology; D003921:Diabetes Mellitus, Experimental / Q000201:enzymology*; D004051:Diethylhexyl Phthalate / Q000494:pharmacology*; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000201:enzymology*; D008297:Male; D010795:Phthalic Acids / Q000494:pharmacology*; D014176:Protein Biosynthesis; D011506:Proteins / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D013217:Starvation / Q000201:enzymology
D000906:Antibodies; D003902:Detergents; D010795:Phthalic Acids; D011506:Proteins; D004051:Diethylhexyl Phthalate; D000217:Acyltransferases; D002334:Carnitine O-Palmitoyltransferase