Effect of physiological levels of caffeine on Ca²⁺ handling and fatigue development in Xenopus isolated single myofibers

Abstract

MC. Effect of physiological levels of caffeine on Ca 2ϩ handling and fatigue development in Xenopus isolated single myofibers. Am J Physiol Regul Integr Comp Physiol 296: R1512-R1517, 2009. First published March 4, 2009 doi:10.1152/ajpregu.90901.2008The purpose of the present study was to determine whether exposure to exogenous physiological concentrations of caffeine influence contractility, Ca 2ϩ handling, and fatigue development in isolated single Xenopus laevis skeletal muscle fibers. After isolation, two identical contractile periods (separated by 60-min rest) were conducted in each single myofiber (n ϭ 8) at 20°C. During the first contractile period, four fibers were perfused with a noncaffeinated Ringer solution, while the other four fibers were perfused with a caffeinated (70 M) Ringer solution. The order was reversed for the second contractile period. The single myofibers were stimulated during each contractile period at increasing frequencies (0.16, 0.20, 0.25, 0.33, 0.50, and 1.0 tetanic contractions/s), with each stimulation frequency lasting 2 min until fatigue ensued, defined in this study as a fall in tension development to 66% of maximum. Tension development and free cytosolic [Ca 2ϩ ] (fura-2 fluorescence spectroscopy) were simultaneously measured. There was no significant difference in the peak force generation, time to fatigue, cytosolic Ca 2ϩ levels, or relaxation times between the noncaffeinated and caffeinated trials. These results demonstrate that physiological levels of caffeine have no significant effect on Xenopus single myofiber contractility, Ca 2ϩ handling, and fatigue development, and suggest that any ergogenic effects of physiological levels of caffeine on muscle performance during contractions of moderate to high intensity are likely related to factors extraneous to the muscle fiber.

In vivo Ca2+ buffering capacity and microvascular oxygen pressures following muscle contractions in diabetic rat skeletal muscles: fiber-type specific effects

“…The rise in resting [Ca 2ϩ ] i following muscle contractions found in the present investigation has also been observed in isolated toad and mouse single muscle fibers from healthy animals (9,44) and is a typical feature of severely fatigued muscle. It was especially interesting that it occurred in the present investigation only in the fast-twitch EDL of diabetic animals, and it did so in the face of increased SERCA protein expression (Fig.…”

In vivo imaging of intracellular Ca2+ after muscle contractions and direct Ca2+ injection in rat skeletal muscle in diabetes

“…Although those mechanisms underlying impaired SR Ca 2ϩ regulatory functions in fatigued skeletal muscle have not been completely elucidated, there is evidence that metabolic perturbations (e.g., ADP, H ϩ , P i , reactive oxygen species) within the cell affect intracellular Ca 2ϩ ([Ca 2ϩ ] i ) (17,23). The observed rise in resting [Ca 2ϩ ] i during muscle fatigue has been observed in isolated toad (43) and mouse single muscle fiber preparations using a lowfrequency fatigue protocol (12). Our recent study has also demonstrated that the resting level of [Ca 2ϩ ] i is increased after tetanic contractions in the in vivo (i.e., circulation intact) muscle preparation model (47,48).…”

The Effect of Caffeine Ingestion on Field Hockey Skill Performance Following Physical Fatigue

“…These effects however, occur only at supraphysiological caffeine doses, impractical for humans; have been demonstrated only in animal-based research (Rosser, Walsh, & Hogan, 2009), and subsequently have been discounted in relation to anaerobically based exercise (Astorino & Roberson, 2010).…”