HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Osterman, A Articles by Arner, A Search for Related Content PubMed PubMed Citation Articles by Osterman, A Articles by Arner, A

Department of Physiology and Biophysics, Lund University, Sweden.

1. The effects of inorganic phosphate (P(i)) on force, Ca(2+)-force relationship, ATPase activity, maximal shortening velocity (Vmax) and rate of tension development were investigated in chemically skinned preparations of smooth muscle from the guinea-pig taenia coli. 2. In maximally thiophosphorylated fibres, P(i) in the range 1-40 mM inhibited isometric force, with a reduction of 20% at 20 mM P(i). 3. The relative force was similar at all [Ca2+], i.e. the Ca(2+)-force relationship was not affected, when 20 mM P(i) was present. 4. After photolytic release of ATP from caged ATP in maximally thiophosphorylated fibres in the presence of 20 mM P(i), tension rose to a lower level but with a higher rate constant than in the absence of P(i). 5. Inorganic phosphate (20 mM) did not affect the ATP hydrolysis in fibres activated at intermediate [Ca2+] or by maximal thiophosphorylation. 6. Inorganic phosphate (20 mM) decreased force but did not influence Vmax in maximally activated fibres. At lower levels of activation by Ca2+, P(i) increased the Vmax and decreased force slightly without affecting the degree of myosin light chain phosphorylation. 7. We conclude that P(i) influences cross-bridge reactions associated with force generation in smooth muscle. These reactions are not rate limiting for cross-bridge turnover under isotonic or isometric conditions in maximally activated smooth muscle fibres, since P(i) did not influence Vmax or the rate of ATP turnover. 8. Since P(i) increased Vmax in submaximally activated muscles, we propose that, under these conditions, shortening velocity is rate limited by cross-bridge states, reached early after attachment, which impose a mechanical resistance to shortening.

This article has been cited by other articles:

				K.-E. Andersson and A. Arner Urinary Bladder Contraction and Relaxation: Physiology and Pathophysiology Physiol Rev, July 1, 2004; 84(3): 935 - 986. [Abstract] [Full Text] [PDF]