AJP - Endocrinology and Metabolism, Vol 262, Issue 2 E167-E172, Copyright © 1992 by American Physiological Society
Relationship between ammonia, heart rate, and exertion in McArdle's disease
J. H. Coakley, A. J. Wagenmakers and R. H. Edwards
Department of Medicine, University of Liverpool, United Kingdom.
We studied plasma ammonia and exercise tolerance in six patients with
McArdle's disease (myophosphorylase deficiency, type V glycogenosis) during
incremental cycle ergometry. Tests were performed either in the
postabsorptive state or after supplementation with branched-chain amino and
2-oxoacids and glucose. Glucose and branched-chain 2-oxoacid combined
increased total work performed from control 49 +/- 22 to 80 +/- 36 kJ (P
less than 0.05). Glucose alone also improved total work performed from 49
+/- 22 to 64 +/- 33 kJ (P less than 0.05). Branched-chain 2-oxoacids alone
had a variable effect, and branched-chain amino acids were of no benefit.
Correlations between plasma ammonia and heart rate for individual patients
were r = 0.99, P less than 0.01; r = 0.95, P less than 0.01; r = 0.84, P
less than 0.01; r = 0.76, P less than 0.01; r = 0.73, P less than 0.01; and
r = 0.63, P less than 0.05 and between ammonia and perceived exertion for
all patients combined was r = 0.70, P less than 0.0001. In two patients,
correlation of ammonia with heart rate at a power output of 60 W was r =
0.91, P less than 0.001 and at 40 W was r = 0.77, P less than 0.001. We
conclude that ammonia is either a mediator or a marker of the metabolic
events leading to fatigue.
