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
218 Alkonyt et al.: Effect of Cold and Fasting on the Carnitine in Adipose Tissue Materials and methods Male Wistar rats weighing 250 — 300 g were used. The animals were exposed to temperatures of 4°, 18° and 20°C for various time periods or they were fasted. The controls were kept at 23 to 24°C. The animals were killed by decapitation, the interscapular brown adipose tissue was frozen in dry ice—acetone mixture. In the experiments each group consisted of 5 to 6 animals. The tissue was extracted with perchloric acid, and carnitine and acetylcarnitine were determined in the extract (Pearson et ah, 1970). The esterified carnitine was liberated by alkaline hydrolysis both in the acid extract (total acid-soluble carnitine) and in the pellet (carnitine esterified with long-chain fatty acids), and was determined as free carnitine. Dry weight was measured after desiccation at 90°C. For lipid-free dry weight determinations lipids were extracted with petroleum ether. The reagents used were CoA, citrate synthetase, malate dehydrogenase, carnitine acetyltransferase (Boehringer, Mannheim, West Germany) NAD, Na-EDTA, Tris, Na-desoxycholate, K0HPO4 (Reanal, Budapest, Hungary). DL-acetylcarnitine was prepared according to Friedman and Fraenkel (1957) from DL-carnitine hydrochloride (Schuchard, Munich, West Germany). Results and discussion After exposing the animals to 4°C for various times there is no increase either in the concentration of long-chain fatty acylcarnitine or in the amount of acetylcarnitine relative to free carnitine (Table 1). The change in the ratio of carnitine ester/free carnitine is an indication of a similar change in the correspond-Table 1 Effect of cold (+4°C) on the concentration of carnitine and carnitine esters in the brown adipose tissue of rats Duration of cold exposure No. of , animals Moles/g wet tissue Non-fat dry materia in % of wet tissue rfc S.E. (No. of animals) long-chain FA carnitine ester ± .S.E. acid soluble* total carnitine ± S.E. . free carnitine ratio ±S.E. Control 0 min6 36+7.25 602+ 19.55 0.29+0.018 11.0+0.04(5)* 30 min 11 23 + 4.08 580+30.15 0.28 + 0.025 1 hour5 23+8.18 565+40.05 i 0.32+0.031 4 hours5 40+9.20 550+42.18 0.31 + 0.035 1 week 15 28+5.85 936+28.20 0.34+0.025 17.6+0.05 (5) 2 weeks5 27+7.87 993 + 49.20 0.27+0.042 16.8+0.04 (5) 4 weeks 10 30+6.12 1083+35.02 0.24+0.034 17.0+0.03 (5) * The total amount of free carnitine and acetylcarnitine is not significantly lower than that of total acid-soluble carnitine Acta Biochimica et Biophysica Academiae Scientiarum Hungaricae 10, 1975