DIURNAL RHYTHM OF THE IN-VIVO ACETATE METABOLISM TO CO2 AND NONSAPONIFIABLE LIPIDS BY NEONATAL CHICK

The in vivo incorporation of acetate into nonsaponifiable lipids was s tudied in different tissues from 14-day-old chick. Total nonsaponifiab le lipids (nmol/30 min/g tissue) were mainly synthesized in testicles and liver. The in vivo CO2 production from acetate by 1-day-old chick did not exhibit diurnal variations. However, in 14-day-old chick, a ma ximal value was observed in the middle of the light period, while a mi nimal value was found 9 h after the start of the dark period. No signi ficant diurnal differences were detected in the in vivo acetate incorp oration into nonsaponifiable lipids by liver and duodenal mucosa from 1-day-old chick. Nevertheless, a clear diurnal rhythm was found in liv er and duodenal mucosa from 14-day-old chick, but not in brain and kid ney from animals of the same age. Distribution of radioactivity from ( 1-C-14)acetate among the different constituents of the nonsaponifiable fraction has been also studied at 3-h intervals. Cholesterol was the major sterol formed from acetate by chick liver at any time of day. In duodenal mucosa and kidney, maximal values in the percentage of chole sterol synthesized were observed during the light period.