Cerebral glucose transport and oxygen consumption in sheep and rabbits

作者：J. R. Pappenheimer, B. P. Setchell · 发表于：The Journal of Physiology · 年份：1973 · DOI：10.1113/jphysiol.1973.sp010322 · 被引用次数：138 · 研究领域：Diet and metabolism studies、Regulation of Appetite and Obesity、Muscle metabolism and nutrition

1. Mechanisms underlying the ability of ruminants to tolerate severe hypoglycaemia have been investigated. Anaesthetized sheep and rabbits were compared with respect to cerebral glucose transport and oxygen consumption as a function of glucose concentration in cerebral extracellular fluids.2. Glucose in plasma was decreased by insulin or increased by I.V. infusion. Measurements were made of cerebral blood flow, arteriovenous concentration differences of glucose and oxygen and the concentration of glucose in c.s.f.3. Equations for carrier-mediated transport accurately described steady-state glucose flux across the blood-brain barrier as plasma concentration was varied from 0.2 to 30 mM. In sheep, the affinity constant (K(m)) was 6 mM and the maximum transport capacity (T(m)) was 260 mumole min(-1). 100 g(1) brain. In rabbits, K(m) = 5.5 mM and T(m) = 280 mumole min(-1). 100 g(1). Transport of glucose across the blood-brain barrier of rabbits is at least as efficient as that in sheep and in both species T(m) is 10-15 times greater than normal rates of glucose utilization.4. During hypoglycaemia the concentration of glucose in c.s.f. is less in sheep than in rabbits (Fig. 5). Steady-state utilization of glucose by sheep brain decreased to 50% of normal when steady-state concentration of glucose in c.s.f. (interstitial fluid) falls to 0.1 mumole ml.(-1); in rabbits the corresponding concentration is 0.7 mumole ml.(-1) (Fig. 6). We suggest that transport capacity of membranes sepa...