Abstract
The effects of vagotomy and sympathectomy upon the diurnal fluctuation of the activity of 3-hydroxy-3-methylglutaryl CoA reductase (HMG-CoA reductase), the key enzyme of cholesterol synthesis, in rat liver were studied. The levels of the active form of the enzyme in sham-operated, hepatic-sympathectomized and vagotomized rats were 3.91±0.21, 3.5±0.15 and 4.9±0.30 nmol/mg protein/h at midday, and 9.64±1.33, 11.60±1.89 and 5.68±0.68 nmol/mg protein/h at midnight, respectively. Thus, bilateral subdiaphragmatic vagotomy suppressed the normal diurnal fluctuation of the reductase activity, whereas hepatic sympathectomy tended to amplify the fluctuation. These results suggest that the diurnal fluctuation of HMG-CoA reductase activity of the liver is under neural influences.
