Ion-specific and general ionic effects on contraction of skinned fast-twitch skeletal muscle from the rabbit.
We used single fibers from rabbit psoas muscle, chemically skinned with Triton X-100 nonionic detergent, to determine the salts best suited for adjusting ionic strength of bathing solutions for skinned fibers. As criteria we measured maximal calcium-activated force (Fmax), fiber swelling estimated optically, and protein extraction from single fibers determined by polyacrylamide gel electrophoresis with ultrasensitive silver staining. All things considered, the best uni-univalent salt was potassium methanesulfonate, while a number of uni-divalent potassium salts of phosphocreatine, hexamethylenediamine N,N,N',N'-tetraacetic acid, sulfate, and succinate were equally acceptable. Using these salts, we determined that changes in Fmax correlated best with variations of ionic strength (1/2 sigma ci z2i, where ci is the concentration of ion i, and zi is its valence) rather than ionic equivalents (1/2 sigma ci magnitude of zi). Our data indicate that increased ionic strength per sc decreases Fmax, probably by destabilizing the cross-bridge structure in addition to increasing electrostatic shielding of actomyosin interactions.
Andrews
M A
MA
Department of Physiology & Endocrinology, Medical College of Georgia, Augusta 30912-3000.
Maughan
D W
DW
Nosek
T M
TM
Godt
R E
RE
D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002412:Cations / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D008698:Mesylates / Q000494:pharmacology; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology*; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D011188:Potassium / Q000494:pharmacology; D011817:Rabbits; D012964:Sodium / Q000494:pharmacology
D002412:Cations; D008698:Mesylates; C045880:methanesulfonic acid; D012964:Sodium; D011188:Potassium; D002118:Calcium