The effects of hypoglycaemia on cerebral blood flow and metabolism in the new-born calf.
1. The effects of insulin hypoglycaemia on cerebral blood flow and metabolism have been examined in unanaesthetized, unrestrained calves between 1 and 26 days after birth. 2. Cerebral blood flow was measured with an inert gas technique using molecular hydrogen, and cerebral metabolism was quantified by determination of arterio-cerebral venous (A--V) concentration differences for oxygen, glucose, lactate, pyruvate, acetoacetate, beta-D-hydroxybutyrate and ammonia. 3. During normoglycaemia the mean (A--V) difference for glucose was close to one sixth that of oxygen, on a molar basis. A small net loss of pyruvate from the brain was found, but there was no significant (A--V) difference for lactate. Arterial concentrations of acetoacetate and beta-D-hydroxybutyrate were low, and no utilization of ketone bodies by the brain was demonstrated. 4. Moderate hypoglycaemia (arterial plasma glucose concentration 1--2 m-mole/l.) had no measurable effect on either cerebral blood flow or metabolism. 5. During profound hypoglycaemia (arterial plasma glucose concentration less than 1.0 m-mole/l.) cerebral glucose uptake was sufficient to account for only 56% of the cerebral oxygen consumption. Cerebral oxygen consumption fell in comatose animals, but increased during hypoglycaemic convulsions, as did cerebral blood flow. 6. In day-old calves hypoglycaemia was associated with a rise in blood lactate concentration and uptake of lactate by the brain. 7. A net loss of ammonia by the brain was observed during hypoglycaemia in calves at all ages examined. The loss was greater in convulsing than in comatose animals.
D000641:Ammonia / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000378:metabolism* / Q000502:physiology; D001786:Blood Glucose / Q000378:metabolism; D001921:Brain / Q000378:metabolism*; D002417:Cattle; D002560:Cerebrovascular Circulation; D005947:Glucose / Q000378:metabolism; D007003:Hypoglycemia / Q000378:metabolism* / Q000503:physiopathology; D007328:Insulin; D007773:Lactates / Q000378:metabolism; D010101:Oxygen Consumption
D001786:Blood Glucose; D007328:Insulin; D007773:Lactates; D000641:Ammonia; D005947:Glucose