1. The relationships between food intake self-selection and liver substrates (glycogen, fat) or activities of pyruvate kinase, glucose-6-phosphate dehydrogenase, malic enzyme, acetyl CoA carboxylase, ...glucose-6-phosphatase and phosphoenolpyruvate carboxykinase were determined during the spontaneous variations of body weight in the dormouse. 2. The results show that during the phase of increasing body weight, carbohydrate intake and enzyme activities involved in lipogenesis are on a high level. 3. On the last part of the body weight increasing phase, when lipid intake occurs, lipogenesis is depressed and a gluconeogenetic activity is set on, while total caloric intake is important and body weight is still increasing. 4. These metabolic changes are interpreted as a preparation to hibernating conditions in the dormouse.
Gluconeogenic enzymes and substrates were measured in the livers of fasted and suckled newborn pigs in the first 48 h postpartum. The activities at birth of glucose-6-phosphatase, ...fructose-1,6-diphosphatase, pyruvate carboxylase and phosphoenolpyruvate carboxykinase were, respectively, 70%, 45%, 117% and 35% of adult values. At birth, cytosolic phosphoenolpyruvate carboxykinase represented 35% of total activity, a similar distribution to that in the adult. In suckled piglets, all activities were greater at 24 and 48 h that at birth. In starved piglets, the increases were greater in all cases; the increase in cytosolic phosphoenolpyruvate carboxykinase was much more pronounced than for that for the particulate enzyme, with the former representing more than 50% of total at 48 h. The levels of gluconeogenic enzymes in the piglets in the early neonatal period would appear to be adequate for their needs and do not provide an explanation for their fasting hypoglycaemia. Hepatic levels of lactate, pyruvate, phosphoenolpyruvate, ketone bodies, and amino acids were determined in these piglets. No significant differences were observed in these metabolites between fasted and suckled animals except that glutamine was doubled in fed piglets, Evidence for the metabolic block in the livers of fasted animals was lacking and ketone bodies did not accumulate. These observations suggest that the limitations to gluconeogenesis result from unavailability of energy substrates and/or carbon precursors to the liver or the deficiency in their uptake.
The influence of the dose, as well as the application area of topically applied 3H-estradiol in a volatile solution on its systemic bioavailability was investigated in hairless rats in vivo. The ...bioavailability was determined by comparing the urinary and fecal excretion of radioactivity after intravenous injection and after topical application. Whatever the size of the surface of application (1, 4 or 16 cm2), the bioavailability was similar (47-65%) 4 days after the application of a single low dose (50 nmol). When the surface of application was washed 24 h after dosing, the absorption was the same for the areas of 3 and 9 cm2. In all cases average fluxes on the first day were higher for the larger area. When applied doses were increased (1,000 and 10,000 nmol), the percentage of percutaneous absorption decreased with the reduction in the areas of application. Thus, with a dose of 1,000 nmol applied on a surface of 1, 4 and 16 cm2, absorption was equal to 18.7, 21 and 37%, respectively, of the dose. There was a linear relationship between the log of the dose applied per unit of skin area and the percentage of absorption after 4 days (r = 0.99 with washing; r = 0.98 without washing).
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