caa a22 4500 475745353 CHVBK 20180406123511.0 cr unu---uuuuu 170329e20000701xx s 000 0 eng 10.1023/A:1005650425513 doi (NATIONALLICENCE)springer-10.1023/A:1005650425513 Intracellular calcium during fatigue of cane toad skeletal muscle in the absence of glucose [Elektronische Daten] [A. Kabbara, L. Nguyen, G. Stephenson, D. Allen] Mechanisms of fatigue were studied in single muscle fibres of the cane toad (Bufo marinus) in which force, intracellular calcium ([Ca2+]i), [Mg2+]i, glycogen and the rapidly releasable Ca2+ from the sarcoplasmic reticulum (SR) were measured. Fatigue was produced by repeated tetani continued until force had fallen to 50%. Two patterns of fatigue in the absence of glucose were studied. In the first fatigue run force fell to 50% in 8-10 min. Fatigue runs were then repeated until force fell to 50% in <3 min in the final fatigue run. Addition of extracellular glucose after the final fatigue run prolonged a subsequent fatigue run. In the first fatigue run peak tetanic [Ca2+]i initially increased and then declined and at the time when force had fallen to 50% tetanic [Ca2+]i was 54 ± 5% of initial value. In the final fatigue run force and peak tetanic [Ca2+]i declined more rapidly but to the same level as in first fatigue runs. At the end of the first fatigue run, the rapidly releasable SR Ca2+ store fell to 46 ± 6% of the pre-fatigue value. At the end of the final fatigue run the rapidly releasable SR Ca2+ store was 109 ± 16% of the pre-fatigue value. In unstimulated fibres the nonwashable glycogen content was 176 ± 30 mmol glycosyl units/l fibre. After one fatigue run the glycogen content was 117 ± 17 mmol glycosyl units/l fibre; at the end of the final fatigue run the glycogen content was reduced to 85 ± 9 mmol glycosyl units/l fibre. [Mg2+]i did not change significantly at the end of fatigue in either the first or the final fatigue run suggesting that globally-averaged ATP does not decline substantially in either pattern of fatigue. These results suggest that different mechanisms are involved in the decline of tetanic [Ca2+]i in first compared to final fatigue runs. The SR Ca2+ store is reduced in first fatigue runs; this is not the case for the final fatigue run which is associated with a decline in glycogen and possibly related to either a non-metabolic effect of glycogen or a spatially-localised metabolic decline. Kluwer Academic Publishers, 2000 Kabbara A. Department of Physiology and Institute of Biomedical Science, University of Sydney F13, 2006, NSW, Australia aut Nguyen L. School of Life Sciences and Technology, Victoria University of Technology, 8001, Footscray, Victoria, Australia aut Stephenson G. School of Life Sciences and Technology, Victoria University of Technology, 8001, Footscray, Victoria, Australia aut Allen D. Department of Physiology and Institute of Biomedical Science, University of Sydney F13, 2006, NSW, Australia aut Journal of Muscle Research & Cell Motility Kluwer Academic Publishers 21/5(2000-07-01), 481-489 0142-4319 21:5<481 2000 21 10974 https://doi.org/10.1023/A:1005650425513 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1023/A:1005650425513 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Kabbara A. Department of Physiology and Institute of Biomedical Science, University of Sydney F13, 2006, NSW, Australia aut NATIONALLICENCE 700 1- Nguyen L. School of Life Sciences and Technology, Victoria University of Technology, 8001, Footscray, Victoria, Australia aut NATIONALLICENCE 700 1- Stephenson G. School of Life Sciences and Technology, Victoria University of Technology, 8001, Footscray, Victoria, Australia aut NATIONALLICENCE 700 1- Allen D. Department of Physiology and Institute of Biomedical Science, University of Sydney F13, 2006, NSW, Australia aut NATIONALLICENCE 773 0- Journal of Muscle Research & Cell Motility Kluwer Academic Publishers 21/5(2000-07-01), 481-489 0142-4319 21:5<481 2000 21 10974 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer