caa a22 4500 469054441 CHVBK 20180323132839.0 cr unu---uuuuu 170328e19920501xx s 000 0 eng 10.1007/BF00705093 doi (NATIONALLICENCE)springer-10.1007/BF00705093 Adenine nucleotide degradation in the thoroughbred horse with increasing exercise duration [Elektronische Daten] [Dean Sewell, Roger Harris] Summary: Adenine nucleotide (AN) degradation has been shown to occur during intense exercise in the horse and in man, at or close to the point of fatigue. The aim of the study was to compare the concentrations of muscle inosine 5′-monophosphate (IMP) and plasma ammonia (NH3) during intense exercise with the concentrations of muscle and blood lactate. Seven trained thoroughbred horses were used in the study. Each exercised on a treadmill for periods of between 30 s and 150 s, at 11 and/or 12 m · s−1. Blood and muscle samples were taken and analysed for lactate and NH3 and adenosine 5′-triphosphate (ATP), phosphorylcreatine (PCr), IMP, creatine, lactate and glycerol-3-phosphate respectively. Horses showed varying degrees of AN degradation as indicated by plasma [NH3] and muscle [ATP] and [IMP]. Comparisons of [IMP] with muscle [lactate], and plasma [NH3] with that of blood [lactate] indicated a threshold to the start of AN degradation. This threshold corresponded to a lactate content of around 80 mmol · kg−1 dry muscle and 15 mmol · l−1 in blood. We discuss the mechanisms which have been proposed to account for AN degradation and suggest that IMP formation occurs as a result of a sudden rise in the concentration of adenosine 5′-diphosphate (ADP) and consequently the concentration of adenosine 5′-monophosphate. The data suggest a critical pH below which there may be a substantial reduction in the kinetics of ADP rephosphorylation provided by PCr resulting in an increase in [ADP], which is the stimulus to AN degradation during intense exercise. Springer-Verlag, 1992 Ammonia nationallicence Inosine monophosphate nationallicence Equine nationallicence Exercise nationallicence Adenosine monophosphate-deaminase nationallicence Sewell Dean Department of Physiology, The Animal Health Trust, P.O. Box 5, CB8 7DW, Newmarket, Suffolk, UK aut Harris Roger Department of Physiology, The Animal Health Trust, P.O. Box 5, CB8 7DW, Newmarket, Suffolk, UK aut European Journal of Applied Physiology and Occupational Physiology Springer-Verlag 65/3(1992-05-01), 271-277 0301-5548 65:3<271 1992 65 421 https://doi.org/10.1007/BF00705093 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/BF00705093 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Sewell Dean Department of Physiology, The Animal Health Trust, P.O. Box 5, CB8 7DW, Newmarket, Suffolk, UK aut NATIONALLICENCE 700 1- Harris Roger Department of Physiology, The Animal Health Trust, P.O. Box 5, CB8 7DW, Newmarket, Suffolk, UK aut NATIONALLICENCE 773 0- European Journal of Applied Physiology and Occupational Physiology Springer-Verlag 65/3(1992-05-01), 271-277 0301-5548 65:3<271 1992 65 421 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer