Adipose tissue extracts plasma ammonia after sprint exercise in women and men

Adipose tissue extracts plasma ammonia after sprint exercise in women and men. J Appl Physiol 101: 1576-1580, 2006. First published November 10, 2005; doi: 10.1152/japplphysiol.01119.2004-This study evaluates a possible contribution of adipose tissue to the elimination of plasma ammonia (NH3) after high-intensity sprint exercise. In 14 healthy men and women, repeated blood samples for plasma NH3 analyses were obtained from brachial artery and from a subcutaneous abdominal vein before and after three repeated 30-s cycle sprints separated by 20 min of recovery. Biopsies from subcutaneous abdominal adipose tissue were obtained and analyzed for glutamine and glutamate content. After exercise, both arterial and abdominal venous plasma NH3 concentrations were lower in women than in men (P < 0.01 and P < 0.001, respectively). All postexercise measurements showed sex-independent positive arterio-subcutaneous abdominal venous plasma NH3 concentration differences (a-V-abd), indicating a net uptake of NH3 from blood to adipose tissue. However, the fractional extraction (a-V-abd/a) of NH3 was higher in women than in men (P < 0.05). The glutamine-to-glutamate ratio in adipose tissue was increased after the second and third bout of sprint exercise (2.2 +/- 0.7 and 1.6 +/- 0.8, respectively) compared with the value at rest (1.2 +/- 0.6), suggesting a reaction of the extracted NH3 with glutamate resulting in its conversion to glutamine. Adipose tissue may thus play an important physiological role in eliminating plasma NH3 and thereby reducing the risk of NH3 intoxication after high-intensity exercise.