Coenzyme A in the livers of young lambs, adult sheep and rats

Adenosine-triphosphatase activity and nicotinamide nucleotide coenzymes in the parotid gland of the young lamb and adult sheep

1. The activity of a Mg(2+)-dependent Na(+)-plus-K(+)-activated adenosine triphosphatase and the concentrations of nicotinamide nucleotide coenzymes have been measured in the immature parotid glands of young lambs and in the actively secreting glands of adult sheep. 2. The activity of the adenosine triphosphatase increased during development and attained relatively high levels in the mature secreting gland. 3. A high ([NAD]+[NADH(2)])/([NADP]+[NADPH(2)]) ratio (approx. 10:1) was observed in the parotid glands of lambs and sheep. 4. The high concentrations of NAD and the very low concentrations of NADPH(2) have been discussed in relation to metabolic activity, the activity of the Na(+)-plus-K(+)-activated adenosine triphosphatase and the secretion of saliva by the parotid gland.

Aspects of carnitine ester metabolism in sheep liver

1. Carnitine acetyltransferase (EC 2.3.1.7) activity in sheep liver mitochondria was 76nmol/min per mg of protein, in contrast with 1.7 for rat liver mitochondria. The activity in bovine liver mitochondria was comparable with that of sheep liver mitochondria. Carnitine palmitoyltransferase activity was the same in both sheep and rat liver mitochondria. 2. The [free carnitine]/[acetylcarnitine] ratio in sheep liver ranged from 6:1 for animals fed ad libitum on lucerne to approx. 1:1 for animals grazed on open pastures. This change in ratio appeared to reflect the ratio of propionic acid to acetic acid produced in the rumen of the sheep under the two dietary conditions. 3. In sheep starved for 7 days the [free carnitine]/[acetylcarnitine] ratio in the liver was 0.46:1. The increase in acetylcarnitine on starvation was not at the expense of free carnitine, as the amounts of free carnitine and total acid-soluble carnitine rose approximately fivefold on starvation. An even more dramatic increase in total acid-soluble carnitine of the liver was seen in an alloxan-diabetic sheep. 4. The [free CoA]/[acetyl-CoA] ratio in the liver ranged from 1:1 in the sheep fed on lucerne to 0.34:1 for animals starved for 7 days. 5. The importance of carnitine acetyltransferase in sheep liver and its role in relieving ;acetyl pressure' on the CoA system is discussed.

Transport and metabolism of fatty acids by isolated rumen epithelium

1. The metabolism of even-numbered saturated (acetic acid to stearic acid) and unsaturated (oleic acid and linolenic acid) fatty acids by diaphragms of isolated rumen epithelium has been investigated. 2. When fatty acids are presented to the papillae surface, ketone bodies are released from the opposite (muscle) side of the tissue. 3. When the concentration of octanoate or decanoate is increased to a critical value, which varies inversely with the chain length of the fatty acid, the respiration of the tissue is inhibited and ketone body synthesis is diminished. Under these conditions unmetabolized fatty acid crosses the tissue down a concentration gradient. 4. The inhibitions by octanoate and decanoate are more marked when the fatty acid is presented to both surfaces of the rumen epithelium. 5. During the oxidation of octanoate and decanoate at non-inhibitory concentrations, small quantities of shorter chain fatty acids, including acetate, are produced.