Protein Passage Across Cell Membranes

Proceedings of a symposium bringing together researchers using microelectrodes and dye markers for specific ions to discuss the control of cellular pH in muscle and nerve cells and the mechanisms of acid transport across epithelial membranes and ion currents across other membranes.

---

Proton Passage Across Cell Membranes Chairman: R. C. Thomas 1988 The control of intracellular pH is of vital importance to every living cell. This is reflected in both the diversity of systems covered within this book and their underlying similarities. Proton movement across cell membranes is achieved either by exchange for another cation or by anionic co-transport, which in turn may be direct or indirect and occur by a specific transport mechanism or by non-ionic diffusion. Whereas many transport systems were thought to be unique to the kidney, these are now being identified in a variety of cell types; their characteristics in these cells are described, including the search for inhibitors specific for each system. It is emphasized that pH homeostasis cannot be regarded as an isolated phenomenon. In nerve cells, ion movements must be regulated so that membrane potential is maintained for signal transmission; in muscle, force generation leads to the production of lactic acid, which must be eliminated; in the kidney, pH may in turn control salt excretion by the asymmetric distribution of different transporters on opposing cell membranes.
There is also an interaction between proton concentrations and calcium ions, the latter acting as a second messenger for many signalling processes. The importance of pH in the action of hormones and growth factors is discussed. The development of more sensitive microelectrodes has enabled more accurate recordings to be made of pH inside and outside the cell and at the surface of the membrane. The electrophysiological studies are correlated with visual evidence from electron microscopy and the actual components of the transporters are identified using the techniques of molecular biology. Together these aspects all contribute to a greater understanding of the mechanisms of proton transport and intracellular pH regulation. Related Ciba Foundation Symposia: No 122 Calcium and the cell Chairman: P. F. Baker 1986 ISBN 0 471 91088 0 No 125 Junctional complexes of epithelial cells Chairman: Sir Micheal Stoker 1987 ISBN 0 471 91091 0