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

Abstract

Jansson. 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 (NH 3) after high-intensity sprint exercise. In 14 healthy men and women, repeated blood samples for plasma NH 3 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 NH 3 concentrations were lower in women than in men (P Ͻ 0.01 and P Ͻ 0.001, respectively). All postexercise measurements showed sex-independent positive arterio-subcutaneous abdominal venous plasma NH 3 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 Ͻ 0.05). The glutamine-to-glutamate ratio in adipose tissue was increased after the second and third bout of sprint exercise (2.2 Ϯ 0.7 and 1.6 Ϯ 0.8, respectively) compared with the value at rest (1.2 Ϯ 0.6), suggesting a reaction of the extracted NH 3 with glutamate resulting in its conversion to glutamine. Adipose tissue may thus play an important physiological role in eliminating plasma NH 3 and thereby reducing the risk of NH 3 intoxication after high-intensity exercise. glutamine; glutamate; biopsy; sex; Wingate test HIGH-INTENSITY SPRINT EXERCISE induces a pronounced breakdown of ATP in skeletal muscle and a corresponding increase of inosine monophosphate (IMP) as a result of subsequent deamination of AMP. A portion of the ammonia/ammonium (NH 3 ) produced in this deamination process is released into the blood. The removal of NH 3 from the blood is of significant physiological importance (2, 22) because high plasma NH 3 concentration causes negative effects like vomiting and impairment of the central nervous system and motor functioning.We recently showed that the degree of muscle ATP net breakdown in skeletal muscle per unit muscle mass and the concomitant increase in IMP generation during high-intensity sprint exercise does not differ between women and men either in type I (slow) or in type II (fast) fibers (9 -11). However, in this situation, plasma NH 3 concentrations reach much lower levels in women than in men, despite the fact that IMP and NH 3 are formed in equal quantities per unit muscle mass during deamination of AMP. To some extent, however, the sex difference in plasma NH 3 may depend on the smaller skeletal muscle mass (relative to body size) in women than in men.

Beyond water homeostasis: Diverse functional roles of mammalian aquaporins

“…It has been shown in humans that during intense exercise, adipose tissue removes ammonia from the plasma and increases its glutamine/glutamate ratio [106], suggesting incorporation of ammonia into glutamine through glutamine synthase as a secondary detoxification pathway in support of the hepatic urea cycle at times of elevated plasma ammonia. Whether AQP7 contributes to this ammonia uptake is yet to be investigated.…”

Sex alters impact of repeated bouts of sprint exercise on neuromuscular activity in trained athletes

“…Since we postulated that the sex difference in mechanical output decrement might be influenced by sex-specific neuromuscular adjustments, an additional observation needs to be emphasised. A greater clearance of ammonia from the blood has been demonstrated in women, compared with men, during repeated 30-s sprints (Esbjörnsson et al 2006). It has been hypothesized that the subsequent lower accumulation of plasma ammonia in women explains the observed sex difference in muscle fatigue during sprints (Esbjörnsson et al 2006).…”

“…A greater clearance of ammonia from the blood has been demonstrated in women, compared with men, during repeated 30-s sprints (Esbjörnsson et al 2006). It has been hypothesized that the subsequent lower accumulation of plasma ammonia in women explains the observed sex difference in muscle fatigue during sprints (Esbjörnsson et al 2006). Since ammonia impairs central nervous system (CNS) and motor functioning (Nybo and Secher 2004), this mechanism constituted an additional argument to examine the potential role of neuromuscular activity as a contributor to the sex difference in performance during repeated bouts of sprint exercise.…”

Avaliação da glutamina, amônia e cortisol em cavalos de enduro durante corridas de diferentes distâncias

“…A remoção da amônia do sangue é de fundamental importância, pois o seu acú-mulo prejudica as funções motoras e o sistema nervoso central. Durante o exercício, os tecidos adiposo e muscular, ricos em enzima glutamina sintase, são os maiores responsáveis pela remoção da amônia e a utilizam, juntamente com o glutamato, para produzir glutamina (ESBJÖRNSSON et al, 2006).…”