Influence of inorganic phosphate and pH on sarcoplasmic reticular ATPase in skinned muscle fibres of Xenopus laevis

G. J.M. Stienen, Z. Papp, R. Zaremba

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

1. The influence of 30 mM inorganic phosphate (P(i)) and pH (6.2-7.4) on the rate of ATP utilization was determined in mechanically skinned bundles of myofibrils from the iliofibularis muscle of Xenopus laevis at approximately 5°C. 2. BDM (2,3-butanedione monoxime; 10 mM) depressed isometric force production and actomyosin (AM) ATPase activity equally. Therefore sarcoplasmic reticular (SR) ATPase activity could be determined by extrapolation of the total ATPase activity to zero force. 3. The SR ATPase activity without added P(i) at pH 7.1 was 42 ± 2% of the total ATPase activity. Addition of 30 mM P(i) reduced SR ATPase activity slightly, by 9 ± 5%, and depressed force by 62 ± 2% and AM ATPase activity by 21 ± 6%. 4. At pH 6.2, force, SR ATPase activity and AM ATPase activity were reduced by 21 ± 5, 61 ± 5 and 10 ± 4% of their respective values at pH 7.1. 5. The SR ATPase activity at 30 mM P(i) and pH 6.2 was reduced markedly to 20 ± 6% of the value under control conditions, suggesting that the maximum rate of Ca2+ uptake during muscle fatigue was strongly depressed. This reduction was larger than expected on the basis of the effects of P(i) and pH alone.

Original languageEnglish
Pages (from-to)735-744
Number of pages10
JournalJournal of Physiology
Volume518
Issue number3
DOIs
Publication statusPublished - Aug 1 1999

ASJC Scopus subject areas

  • Physiology

Fingerprint Dive into the research topics of 'Influence of inorganic phosphate and pH on sarcoplasmic reticular ATPase in skinned muscle fibres of Xenopus laevis'. Together they form a unique fingerprint.

  • Cite this