Orally administered [14C]DPA and [14C]DHA are metabolised differently to [14C]EPA in rats

Previous studies have revealed that C20 PUFA are significantly less oxidised to CO2 in whole-body studies compared with SFA, MUFA and C18 PUFA. The present study determined the extent to which three long-chain PUFA, namely 20 : 5n-3 EPA, 22 : 5n-3 docosapentaenoic acid (DPA) and 22 : 6n-3 DHA, were catabolised to CO2 or, conversely, incorporated into tissue lipids. Rats were administered a single oral dose of 2·5 μCi [1-14C]DPA, [1-14C]EPA, [1-14C]DHA or [1-14C]oleic acid (18 : 1n-9; OA), and were placed in a metabolism chamber for 6 h where exhaled 14CO2 was trapped and counted for radioactivity. Rats were euthanised after 24 h and tissues were removed for analysis of radioactivity in tissue lipids. The results showed that DPA and DHA were catabolised to CO2 significantly less compared with EPA and OA (P< 0·05). The phospholipid (PL) fraction was the most labelled for all three n-3 PUFA compared with OA in all tissues, and there was no difference between C20 and C22 n-3 PUFA in the proportion of label in the PL fraction. The DHA and DPA groups showed significantly more label than the EPA group in both skeletal muscle and heart. In the brain and heart tissue, there was significantly less label in the cholesterol fraction from the C22 n-3 PUFA group compared with the C20 n-3 PUFA group. The higher incorporation of DHA and DPA into the heart and skeletal muscle, compared with EPA, suggests that these C22 n-3 PUFA might play an important role in these tissues.

A Method Based on the Roller Chamber Technique for Determination of CO2 Production in Cultured Cells: Effects of Acrylamide in Neuroblastoma N1E115 Cultures

The effects of acrylamide on CO2 production from [14C]-labelled glucose, pyruvate and glutamine have been studied in a mouse neuroblastoma cell line C1300, clone N1E115. A rotation metabolism chamber, permitting closed incubation of monolayer, anchorage-dependent cell cultures under good physiological conditions, was developed for making the determinations. The cells were exposed to acrylamide (0.35mM) for 14 days. The total amunt of CO2 produced from glucose and pyruvate was increased by exposure to acrylamide, whereas a slight inhibition was found in the production from glutamine. The production of lactate remained unchanged. Comparison of these results with other data obtained in our laboratory leads us to conclude that the method described is relevant for the determination of energy metabolic processes through the quantification of CO2 production. Furthermore, we assume that acrylamide causes an increased demand for energy in the cells and that this demand is met by the cells through the increased oxidative phosphorylation of glucose.

Differential oxidation of saturated and unsaturated fatty acids in vivo in the rat

1. The oxidation rates of lauric, myristic, palmitic, stearic, oleic, α-linolenic, linoleic, γ-linolenic, dihomo- γ-linolenic and arachidonic acids were studied by use of a radioisotope tracer technique in weanling rats at rest in a metabolism chamber over 24 h.2. Of the saturated fatty acids, lauric acid (12:O) was the most efficient energy substrate: the longer the chain length of the saturated fatty acids, the slower the rate of oxidation.3. Oleic acid (18:1) was oxidized at a remarkably fast rate, similar to that of lauric acid.4. Of the ω6 essential fatty acids studied, linoleic acid (18:2ω6) was oxidized at a faster rate than any of its metabolites, with arachidonic acid (20:4ω6) being oxidized at the slowest rate.5. The rate of oxidation of γ-linolenic acid (18:3ω3) was almost as fast as that of lauric and oleic acids.

Role of epinephrine for muscular glycogenolysis and pancreatic hormonal secretion in running rats

We have previously shown that during swimming muscular glycogen breakdown was diminished and plasma glucagon and insulin were lower and higher, respectively, in adrenodemedullated rats compared to controls. These findings might be due to a lower work intensity or higher efficiency in adrenodemedullated rats than in controls. Furthermore, they might be due to either an acute or a chronic influence of epinephrine. Rats were adrenodemedullated (DM) or sham-operated (C). They were chronically cannulated and either rested or ran in a metabolism chamber for 45 min. Running DM rats had either saline (DM-S) or epinephrine (normalizing the concentration in plasma) (DM-E) infused. During running, oxygen uptake was identical in C and DM rats. Muscular glycogen breakdown was similar in DM-E and C rats and higher than in DM-S rats. Blood glucose, lactate, and heart rate increased in C and DM-E, but not in DM-S rats. In spite of the differences in blood glucose, plasma insulin was the same in all groups and plasma glucagon increased identically in all running rats. Plasma FFA and liver glycogen were similar in all groups. In conclusion. in running rats, epinephrine exerts an acute enhancing effect on muscular glycogenolysis, glucagon secretion, and heart rate and an acute depressing effect on insulin secretion.