The Effect of Porta‐caval Anastomosis Upon the Energy State and Upon Acid‐base Parameters of the Rat Brain

In order to evaluate the influence of porta‐caval anastomosis upon the energy state of the brain, lightly anaesthetized rats were studied either 1 or 5 weeks after the shunting procedure and the brains (frontal lobe, cerebellum and brainstem) were analysed for carbohydrate substrates and organic phosphates. The ammonia contents of arterial blood, cerebrospinal fluid (CSF) and tissue increased progressively in the shunted groups and at 5 weeks the increases were three‐ to six‐fold. In all brain structures studied there were decreases in the glucose and in the aspartate contents but regional differences existed for glucose‐6‐phosphate, α‐ketoglutaratc and glutamate. In the brainstem the tissue contents of glucose‐6‐phosphate and α‐ketoglutarate fell while glutamate was unchanged. Calculation of the cytoplasmatic redox state from the lactate dehydrogenase (LDH) and the malate dehydrogenase (MDH) equilibria indicated that the NADH/NAD+ ratio increased in the shunted groups. However, since there was no significant fall in the calculated adenylate energy charge, it is concluded that porta‐caval anastomosis, and the accompanying hyperammonemia, do not disrupt the balance between production and utilization of energy in the brain.