Acta Biochimica et Biophysica 10. (1975)

1975 / 3. szám - Alkonyi, I.-Kerner, J.-Sándor, A.: The Effect of Cold and Fasting on the Carnitine Concentration in the Brown Adipose Tissue of Rats

Acta Biochim. et Biophys. Acad. Set. Hung. Vol. 10 (3), pp. 217— 220 (1975) The Effect of Cold and Fasting on the Carnitine Concentration in the Brown Adipose Tissue of Rats I. Alkonyi, J. Kerner, A. Sándor Biochemical Institute, University Medical School, Pécs, Hungary (Received September 18, 1974) The ratio of acetylcarnitine to carnitine was unchanged in the interscapular brown fatty tissue of rats which were kept at 5°C. The quantity of total acid soluble carnitine relative to the fat-free dry weight was also unchanged. On the other hand a small decrease of the environmental temperature from 23°C to 18°C and 20°C resulted in a significant increase in the acetylcarnitine to carnitine ratio. A number of data point to a close connection between carnitine content and rate of degradation of fat: carnitine markedly increases the oxidation of fatty acids in various tissue preparations (Fritz, 1959; Fritz, Yue, 1963; Bremer, 1962), and the amount of carnitine esters rises considerably under various conditions characterized by enhanced degradation of fat (Pearson, Tubbs, 1964; Bohmer et al., 1966; Delisle, Radomski, 1968). Carnitine must play a role also in the metab­olism of brown adipose tissue, as here only lipids are oxidized and the oxidation is significantly accelerated in the case of thermogenesis, for example under the effect of cold (Cameron, Smith, 1964; Hull, Segall, 1965). Indeed, it has been shown that the oxygen consumption and fatty acid oxidation of the mitochondria of brown adipose tissue are markedly increased in vitro by carnitine (Hittelman et al., 1969; Drahota et al., 1970). Although the amount of carnitine and the activity of carnitine acetyltransferase (CAT) in brown adipose tissue are high as compared to other tissues (Marquis, Fritz, 1965), it has not yet been studied how these change during the transition from the resting into the thermogenetic phase. Delisle and Radomski (1968) measured the concentration of carnitine and its esters in rats exposed to cold, but omitted from the tissues examined the brown adipose tissue. We have shown in our earlier work that CAT activity increased 2 to 2.5-fold in rat brown adipose tissue during cold adaptation (Kerner et al., 1973). In the present study we examined the concentration of carnitine, acetylcarnitine and long-chain fatty acid carnitine esters under the same experimental conditions. Acta Biochimica et Biophysica Academiae Scientiarum Hungaricae 10, 1975

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