Sarcoplasmic reticulum responses to repeated sprints are affected by conditioning of horses.

Abstract

Sarcoplasmic reticulum (SR) responses to repeated sprints and to physical conditioning were studied in 10 Quarter Horses. Exercise tests (four repeated sprints on a treadmill) were conducted before and after 12 wk of sprint conditioning. Muscle samples from the middle gluteal muscle were taken before and after each exercise test, and SR vesicles were isolated. Calcium uptake was determined spectrophotometrically using antipyrylazo III, and Ca2+-ATPase activity was determined using an enzyme-linked optical assay. Conditioning increased calcium uptake rate and Ca2+-ATPase activity by 14 and 38%, respectively, before exercise and by 25 and 26% after exercise. Exercise decreased calcium uptake rate and Ca2+-ATPase activity by 37 and 27%, respectively, before conditioning and by 28 and 21% after conditioning. Decreases in calcium uptake and Ca2+-ATPase activity of SR have been associated with fatigue during exercise, and this association is strengthened by the moderating effect of conditioning.

Effect of exercise on sarcoplasmic reticulum Ca<sup>2+</sup> transport in muscle of mouse lines long-term selected for different Performance traits

“…Also, the minor differences in Ca 2+ ATPase activities at rest do not lead to the conclusion that the selection had the expected effect on SR Ca 2+ transport. This is in agreement with training experiments, showing an increased Performance but no change in Ca 2+ transport (SEMBROWICH et al, 1978;MADSEN et al, 1994;GREEN et al, 1998), but not with other investigations, indicating a reduced uptake and ATPase activity by long-term training (BELCASTRO, 1987), or an increased uptake and ATPase activity (WILSON et al, 1998), determined at rest. In agreement with the majority of investigations Ca 2+ uptake was affected by the level of exercise.…”

“…Endurance training of rats decreased the Ca 2+ uptake at rest (BELCASTRO, 1987) and a fibre type dependence has been shown (KIM et al, 1981). Sprint conditioning of horses increased the SR Ca 2+ uptake at rest and attenuated an exercise induced decrease in Ca 2+ transport (WILSON et al, 1998). Following endurance training of rats the Ca 2+ uptake of isolated SR was reduced, but not so in muscle homogenates (SEMBROWICH et al, 1978).…”

“…However, Sprint conditioning of horses attenuated the decrease in the calcium transfer rate and in the Ca 2+ ATPase activity (WILSON et al, 1998), and high-resistance training attenuated exercise induced decreases in SR Ca ATPase activity (GREEN et al, 1998). It is suggested that exercise training can retard the onset of fatigue by an attenuation ofa disturbance ofthe Ca 2+ transport (GREEN et al, 1998;WILSON et al, 1998). Selection is another way to influence characters of animals.…”

Variation in expression of calcium-handling proteins is associated with inter-individual differences in mechanical performance of rat (Rattus norvegicus) skeletal muscle

“…An increased density of dihydropyridine and ryanodine receptors in muscle is correlated with increased shortening velocity and force in isolated muscle (Kandarian et al, 1992;Golden et al, 2003;Mänttäri and Järvilehto, 2005), and their density is increased following endurance training in trout (Anttila et al, 2008). SERCA is responsible for calcium reuptake from the cytoplasm to the sarcoplasmic reticulum, and its activity can therefore determine muscle relaxation rate (Fleming et al, 1990;Wilson et al, 1998). SERCA activity is regulated by phosphorylation of phospholamban, which in its unphosphorylated form inhibits SERCA activity (Verboomen et al, 1992;Periasamy and Kalyanasundaram, 2007).…”

Sarcoplasmic Reticulum Ca2+-ATPase Activity and Glycogen Content in Various Fiber Types after Intensive Exercise in Thoroughbred Horses

“…Several studies in horse [2, 34], human [4, 10, 15, 31], and rat [11, 28, 36] have demonstrated that exercise-induced muscle fatigue disturbs SR Ca 2+ handling properties, and the major protein responsible for Ca 2+ uptake is SR Ca 2+ -ATPase. Exercise-induced changes in Ca 2+ uptake results mainly from a shift of catalytic activity of SR Ca 2+ -ATPase [11, 17].…”