Antagonism by phosphate buffer of the twitch loss in isolated muscle fibers produced by calcium-free solutions.
In 37 of 41 isolated frog skeletal muscle fiber preparations (one, two, or three fibers) the twitch was eliminated or reduced to less than 10% of control by exposing the fibers to a O-calcium, bicarbonate-buffered solution for 10 min or less. Replacing the bicarbonate by a phosphate buffer either prevented twitch inhibition or increased the O-calcium exposure time required for its production. It is concluded that surface membrane-bound calcium ions (presumably in the t-tubules) are required to couple the action potential to the mechanical response and that phosphate ions inhibit the loss of the membrane-bound calcium ions into an external calcium-free solution.
D000818:Animals; D001001:Anura; D001639:Bicarbonates / Q000494:pharmacology; D002021:Buffers / Q000494:pharmacology; D002118:Calcium / Q000502:physiology*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D010710:Phosphates / Q000494:pharmacology*; D011894:Rana pipiens; D011896:Rana temporaria
D001639:Bicarbonates; D002021:Buffers; D010710:Phosphates; D002118:Calcium