Propionyl-CoA synthetase in mammary gland and liver of cows.

Propionyl-CoA synthetase of liver and mammary gland from calf and midlactation cow was investigated. No activity of this enzyme was detected in calf mammary gland, but it was detected in calf liver. Propionyl-CoA synthetase was found in both, liver and mammary gland of the cow, although mammary gland activity was about 25% of that found in liver. The effects of pH and temperature on enzyme activity and stability were also investigated in crude extracts of liver and mammary gland tissues. The results suggest a different behaviour of the enzyme from both origins. Kinetic studies of the enzyme were also carried out, showing differences, depending on the organ, in the apparent substrate KM values.

Comparative analysis of propionyl-CoA carboxylase from liver and mammary gland of mid-lactation cow.

1. Propionyl-CoA carboxylase from mid-lactation cow liver and mammary gland has been purified. 2. In both organs, the molecular mass was estimated to be approximately 450 kD, and two molecular subunits of 77 and 64 kD could be observed. 3. Physico-chemical and kinetical properties for the enzyme from both organs were similar, showing an allosteric behaviour in relation to ATP and Mg2+. 4. The presence of propionyl-CoA carboxylase in mid-lactation cow mammary gland with similar properties to the liver enzyme, could indicate the existence of a gluconeogenic metabolism in this organ exactly when a high demand of glucose for milk lactose is required.

Changes in blood glucose, liver glycogen, ketone bodies and plasma insulin in suckling rats treated with a single high cortisol dose one day after birth.

Rats treated with cortisol, 0.5 mg one day after birth, show a decrease in body and organ weight and a decrease in pituitary TSH and GH when compared to controls together with a lack of response of TSH to TRH. These alterations have been previously found in animals treated with large doses of thyroxine, neo-T4 syndrome, in both populations a brain underdevelopment has been observed. Plasma insulin in cortisol-treated animals was higher (P less than 0.01) than in the controls at 8 and 12 days of life and lower at 22 days (P less than 0.001). Plasma ketone bodies were increased significantly at 8 but not at 12 and 22 days of life in the cortisol treated animals. Liver glycogen was higher than in controls at 2, 4, 6 days of life and lower at 8, 12 and 22 days. Blood glucose was higher than in controls at 2, 4 days and lower at 6, 8, 12 and 22 days of life. The timing of metabolic events is important for the adaptation and development of the post-natal animal. The perturbances in carbohydrate metabolism in suckling rats were also previously found in neo-T4 rats during the period when the brain growth spurt and energy need are the greatest; but in the rats treated with cortisol the timing of the alterations was different. This different timing of the metabolic perturbances could correlate with a different maturation in cerebral tissue found in histological studies in the two populations.