INVESTIGATIONS OF THE EFFECTS OF THEOPHYLLINE ADMINISTRATION ON CARNITINE ACETYLTRANSFERASE ACTIVITY OF RAT-HEART

The effects of oral theophylline administration (100 mg/kg b.w./day) o n the activity of carnitine acetyltransferase (CAT) of rat heart for f ive-week interval treatment were studied. The result indicated that th e body weights of placebo groups were not significantly changed as com pared to control groups (P < 0.1), but theophylline treatment caused a significant decrease in the body weights of rat (P < 0.01) as compare d to either control or placebo groups throughout the five-week interva l treatments. Daily administration of theophylline to rats did not sig nificantly affect heart weights as compared to either control or place bo groups (P < 0.1) for the five week-interval treatments. Our data in dicated that the activity of CAT was not significantly changed in plac ebo groups as compared to control groups (P < 0.1), however, there was a significant increase in the activity of CAT in heart of theophyllin e-treated groups (P < 0.01) as compared to either control or placebo g roups. The increase in the activity of CAT was noticed in the first th ree weeks of theophylline treatments followed by a gradual return towa rd normal activity by the fourth and fifth weeks of continued treatmen t. The observed changes in activity of CAT of heart might be due to th eophylline-enhanced mobilization of lipid from adipose tissues which c onsequently stimulated increased L-carnitine transport into the heart tissues to form fatty acyl-carnitine groups for subsequent P-oxidation inside the heart mitochondria. Accumulations of acyl-carnitine groups in heart mitochondria may increase the catalytic action of CAT and po ssible mechanisms are discussed.