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1. The activities in rat tissues of 3-oxo acid CoA-transferase (the first enzyme involved in acetoacetate utilization) were found to be highest in kidney and heart. In submaxillary and adrenal glands the activities were about one-quarter of those in kidney and heart. In brain it was about one-tenth and was less in lung, spleen, skeletal muscle and epididymal fat. No activity was detectable in liver. 2. The activities of acetoacetyl-CoA thiolase were found roughly to parallel those of the transferase except for liver and adrenal glands. The high activity in the latter two tissues may be explained by additional roles of thiolase, namely, the production of acetyl-CoA from fatty acids. 3. The activities of the two enzymes in tissues of mouse, gerbil, golden hamster, guinea pig and sheep were similar to those of rat tissues. The notable exception was the low activity of the transferase and thiolase in sheep heart and brain. 4. The activities of the transferase in rat tissues did not change appreciably in starvation, alloxan-diabetes or on fat-feeding, where the rates of ketone-body utilization are increased. Thiolase activity increased in kidney and heart on fat-feeding. 5. The activity of 3-hydroxybutyrate dehydrogenase did not change in rat brain during starvation. 6. The factors controlling the rate of ketone-body utilization are discussed. It is concluded that the activities of the relevant enzymes in the adult rat do not control the variations in the rate of ketone-body utilization that occur in starvation or alloxan-diabetes. The controlling factor in these situations is the concentration of the ketone bodies in plasma and tissues.

We studied the occurrence, clinical manifestations, and mechanism of hypoglycemia in patients with falciparum malaria in eastern Thailand. Hypoglycemia, which was often severe and recurrent, occurred in 17 patients, including 12 in a series of 151 patients with cerebral malaria. Thirty episodes were investigated. Plasma concentrations of insulin and C peptide were inappropriately high, and lactate and alanine concentrations were significantly higher than in patients with falciparum malaria who were normoglycemic (P less than 0.05). Sixteen patients had received quinine; plasma quinine and insulin concentrations were correlated at the time of hypoglycemia (P = 0.007). In seven healthy fasting volunteers intravenous quinine increased the mean plasma insulin concentration (+/- S.D.) from 8.9 +/- 3.1 to 17.1 +/- 8.4 mU per liter (P = 0.02) and reduced the mean plasma glucose concentration from 88 +/- 20 to 68 +/- 23 mg per deciliter (P = 0.002). Our observations indicate that in falciparum malaria quinine-induced insulin secretion may precipitate hypoglycemia, but other factors, including the large glucose requirements of the malaria parasites may also contribute. This important complication, associated with pregnancy and severe disease, must be excluded in all patients with falciparum malaria who have impaired or deteriorating consciousness.

1. The activities of 3-hydroxybutyrate dehydrogenase and 3-oxo acid CoA-transferase in rat brain at birth were found to be about two-thirds of those of adult rat brain, expressed per g wet wt. The activities rose throughout the suckling period and at the time of weaning reached values about three times higher than those for adult brain. Later they gradually declined. 2. At birth the activity of acetoacetyl-CoA thiolase in rat brain was about 60% higher than in the adult. During the suckling period there was no significant change in activity. 3. In rat kidney the activities of the three enzymes at birth were less than one-third of those at maturity. They gradually rose and after 5 weeks approached the adult value. Similar results were obtained with rat heart. 4. The activity of glutamate dehydrogenase (a mitochondrial enzyme like 3-hydroxybutyrate dehydrogenase and 3-oxo acid CoA-transferase) also rose in brain and kidney during the suckling period, but at no stage did it exceed the adult value. 5. Throughout the suckling period the total ketone-body concentration in the blood was about six times higher than in adult fed rats, and the concentration of free fatty acids in the blood was three to four times higher. 6. It is concluded that the rate of ketone-body utilization in brains of suckling rats is determined by both the greater amounts of the key enzymes in the tissue and the high concentrations of ketone bodies in the blood. In addition, the low activities of the relevant enzymes in kidney and heart of suckling rats may make available more ketone bodies for the brain.

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