Submitted on October 5, 2004
Accepted on November 7, 2005
Adipose tissue extracts plasma ammonia after sprint exercise in women and men
Mona Esbjornsson1*, Jens Bulow2, Barbara Norman1, Lene Simonsen2, Jacek Nowak1, Olav Rooyackers3, Lennart Kaijser1, and Eva Jansson1
1 Department of Laboratory Medicine, Karolinska Institutet, Stockholm, Sweden
2 Department of Clinical Physiology, Bispebjerg Hospital, Copenhagen, Denmark
3 Department of Anaesthesiology and Intensive Care at the Centre for Surgical Sciences, Karolinska Institutet, Stockholm, Sweden
* To whom correspondence should be addressed. E-mail: mona.esbjornsson{at}labmed.ki.se.
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 minutes 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 post exercise measurements showed gender-independent positive arterio-subcutaneous abdominal venous plasma NH3 differences indicating a net uptake of NH3 from blood to adipose tissue. However, the fractional extraction (a-vabd/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 to 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.
