226 Fit Perf J | Rio de Janeiro | 8 | 3 | 226-232 | May/Jun 2009 Copyright© 2009 por Colégio Brasileiro de Atividade Física, Saúde e Esporte EISSN 1676-5133 Fit Perf J. 2009 May-Jun;8(3):226-32. MODERATE-INTENSITY EXERCISE ASSOCIATED WITH KETOGENIC DIET . A MODEL FOR THE STUDY OF AMMONIA METABOLISM ? Flavio Bachini 1,2 f.bachini@gmail.com João Pedro Saar Werneck-de-Castro 1,3 joaopedrowerneck@pq.cnpq.br Leonardo Cristiano Moretzsohn 1,4 leo.c.moretzsohn@bol.com.br Adriana Bassini-Cameron 1 adriana.bassini@terra.com.br Luiz-Claudio Cameron 1,4,5 cameron@unirio.br doi:10.3900/fpj.8.3.226.e Bachini F, Werneck-de-Castro JPS, Moretzsohn LC, Bassini-Cameron A, CameronL-C. Moderate-intensity exercise associated with ketogenic diet. A model for the study of ammonia metabolism? Fit Perf J. 2009 May-Jun;8(3):226--232. ABSTRACT Introduction: Exercise has been used as a model to study the metabolism of ammonia (NH 3 + NH 4 + ), which is highly toxic to the central nervous system. A ketogenic diet leads to several metabolic adaptations to maintain the ATP/ ADP ratio, including a lack of glycogen reservoirs, the use of amino acids as carbon skeleton donors and increased -oxidation of fatty acids. The formation of ammonia during high-intensity exercise is well studied, but its role in mo- derate-intensity exercise remains unclear. Here we investigate ammonia metabolism during moderate-intensity exercise associated with a ketogenic diet as a model system. Materials and Methods: Athletes (n=7) were physically eva- luated and had their maximum oxygen consumption (VO 2max ) and heart rate (HR max ) determined. The subjects remained on a ketogenic diet 72h prior to exercise. They then exercised for 60min at a power output of 60% of that at VO 2max , and at 70%-75% of HR max . Results: Basal ammonemia increased by 35% due to dietetic modifications, while exercise caused a 250% increase in ammonemia in parallel with this effect. Uremia was increased by 60% due to the ketogenic diet without response to exercise. We measured a 10% increase in serum urate that did not change during the exercise protocol. No changes were found in glycemia or lactatemia. Discussion: Our data suggest that moderate-intensity exercise associated with a ketogenic diet can be used to study the increase in ammonemia and as a model to understand ammonia metabolism during metabolic stress. KEYWORDS Hiperammonemia, Lactate, Urate, Central Nervous System. 1 University Federal of the State of Rio de Janeiro - UNIRIO - Laboratory of Protein Biochemistry - Rio de Janeiro - Brazil 2 University of Trás-os- Montes e Alto Douro - UTAD - Post Graduate Program in Physical Education and Sport - Vila Real - Portugal 3 University Federal of Rio de Janeiro - UFRJ - Department of Bioscience and Physical Activity - Laboratory of Molecular Biology and Exercise - Rio de Janeiro - Brazil 4 University Castelo Branco - UCB - Post Graduate Program in Science of Human Motricity - Rio de Janeiro - Brazil 5 University Federal of Uberlândia - UFU - Institute of Genetics and Biochemistry - Uberlândia - Brazil