Fibre types, enzyme activities and substrate utilisation in skeletal muscles of horses competing in endurance rides

Abstract

Summary Venous blood samples and middle gluteal muscle biopsies were obtained from 21 horses taking part in 100 km or 50 km endurance rides. Group A consisted of seven horses competing over 100 km (four horses completed the ride), Group B consisted of the six horses that were among the 10 best over 50 km while the other eight horses of Group C completed 50 km at a slower speed. Blood lactate, glycerol and creatine kinase increased in all groups while aspartate aminotransferase levels were higher only in Group A. No change was found in blood glucose in Groups B and C while horses in Group A had lower levels after the ride. Neither fibre composition, fibre areas nor enzyme activities differed between the groups. Intramuscular glycogen content was similar before the ride in all groups. After the ride glycogen had decreased only half as much in Group C as compared to Groups A and B. Group C had a higher intramuscular triglyceride content at rest than Group B. The greatest decrease in triglyceride content after the ride was found in Group C. In Groups A and B many Type I, IIA and IIB fibres were glycogen depleted after the ride while in Group C mainly Type I and some Type IIA fibres were depleted. The results of this study show that intramuscular carbohydrate and lipid stores are both important fuels during endurance rides.

Housing-related activity in rats: effects on body weight, urinary corticosterone levels, muscle properties and performance

“…Pure muscle tissue was weighed on a Cahn balance (Cahn 25, Cahn Instruments, Los Angeles, USA) and samples of 1-2 mg were homogenized in ice-chilled 0.1 M potassium buffer (pH 7.3) at a dilution of 1:400. The assay mixtures used for enzyme analyses were: for CS and HAD as described by Essén et al (1980), and for LDH and HK as described by Essén-Gustavsson et al (1984). All measured enzyme activities were expressed as mmol/ kg dry weight/min.…”

Effects on exercise metabolism of varying dietary starch and sugar proportions

“…Muscle enzyme analyses were made after homogenisation of the samples in a 0.1 mol/l phosphate buffert at pH 7.3. Citrate synthase (CS), lactate dehydrogenas (LDH), 3-hydroxyacyl-CoA dehydrogenase (HAD) and hexokinase (HK) activities were analysed fluorometrically at 25°C (Essén et al 1980;Essén-Gustavsson et al 1984). The tissue for glycogen determination was boiled for 2 h in 1 mol/l hydrochloric acid in order to form glucose residues.…”

Carbohydrate metabolism in meat animals

“…The difference between the demand and aerobic production has to be met by anaerobic glycolysis, the end product of which is lactate. This is possible, because the capacity of glycolytic enzymes, at least in equine and porcine muscles, is high enough to support the ATP production that allows maximal rate of ATP consumption (Essén-Gustavsson, Karlström, & Lindholm, 1984;Newsholme & Leech, review 1986;Cutmore, Snow, & Newsholme, 1993;Karlström, 1995) . 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 The aerobic capacity is determined by the capacity of cardiovascular system and muscle related factors, such as fibre composition and mitochondrial density.…”