title: Subcellular distribution of potassium in striated muscles.
abstract: Microanalytical experiments have been performed to answer the question whether the main cellular cation, K+, follows the water distribution in the striated muscle cell or whether K+ follows the distribution of negative fixed charges (beta- and gamma-carboxyl groups of aspartic and glutamic acid residues). Subcellular localization of K and/or of the K surrogates Rb, Cs, and Tl has been investigated by the following methods: Chemical precipitation of K with tetraphenylborate. Autoradiography of alkali-metals and Tl in air-dried and frozen-hydrated preparations. TEM visualization of electron dense Cs and Tl in sections of freeze-dried and plastic embedded muscle. X-ray microanalysis of air-dried myofibrils and muscle cryosections. The experiments consistently show that K, Rb, Cs, and Tl do not follow the water distribution but are mainly accumulated in the A band, especially in the marginal regions, and at Z lines. The same sites preferentially accumulate Cs or uranyl cations when sections of freeze-dried, embedded muscle are exposed to these electron microscopic stains. It is concluded that the detected uneven distribution of K, Rb, Cs, and Tl in muscle is neither a freeze-drying artifact nor an embedding artifact and may result from a weak ion binding to the beta- and gamma-carboxyl groups of cellular proteins.
mesh_terms: D000818:Animals; D001001:Anura; D001345:Autoradiography; D001516:Bees; D011232:Chemical Precipitation; D004577:Electron Probe Microanalysis; D008854:Microscopy, Electron; D009132:Muscles / Q000378:metabolism* / Q000648:ultrastructure; D011188:Potassium / Q000378:metabolism*; D013347:Subcellular Fractions / Q000378:metabolism
chemical_list: D011188:Potassium