No abstract

The effect of propionate on ketone body production from oleate and octanoate in isolated rat hepatocytes was studied. Propionate (5 mmol/l) stimulated ketogenesis from oleate and octanoate, although the effect was more pronounced when octanoate was used as substrate. Propionate decreased CO2 production from fatty acids, suggesting that propionate inhibited the oxidation of free fatty acid carbons through the tricarboxylic acid cycle. Our results suggest that propionate enhanced ketogenesis as a consequence of the decrease in the rate of the tricarboxylic acid cycle, caused by propionate and/or its derivatives. The stimulation of ketogenesis caused by propionate is discussed as the possible cause of ketosis associated with propionic acidaemia and methylmalonic acidaemia.

1. We have analyzed the behavior of two types of asymmetric molecular forms (A forms) of acetylcholinesterase (AChE) during development of chick hindlimb muscle, in vivo and in cell culture, and upon irreversible inactivation of peroneal muscle AChE with diisopropylfluorophosphate (DFP) in vivo. 2. In agreement with previous developmental studies on chick muscle, globular forms of AChE (G forms) are predominant in chick hindlimb at early embryonic ages, being gradually replaced by A forms as hatching (and, therefore, onset of locomotion) approaches. Of the two A-form types, AI appears and accumulates significantly earlier than AII, so that A/G and II/I ratios higher than 1 are attained only at about hatching time. 3. Cultures prepared from 11-day chick embryo hindlimb myoblasts express both types of A forms, with a combined activity of 27% of total AChE after 12 days in culture. AI forms appear again earlier and are much more abundant than type II asymmetric species through the life span of cultures. 4. All AChE activity in the peroneal muscle is irreversibly inactivated by injection of DFP in vivo. The recovery of A forms follows the same sequence described for normal development, with a delayed and slower recovery of AII forms as compared with AI. 5. Several hypotheses involving tail polypeptides or tissue target molecules, or posttranslational interconversion, are proposed to help explain the earlier appearance and accumulation of AI forms in chick muscle.