Introduction: Membrane Transport in Physiology

Abstract

It is remarkable that the very existence of cell membranes was problematic when I and most of the other authors of this volume began our work. Permeability measurements had, of course, given rise to the hypothesis that membranes envelop cells (see chapter by Hugh Dayson). However, it was not until the emergence of the electron microscope, and particularly, adequate techniques for the isolation, purification, and chemical characterization of membranes, that these structures were recognized as essential components of cells and organelles (see chapter by J. David Robertson). Moreover, the development of isotopic tracer and electrical methods during the 1940s and 1950s made possible a more quantitative description of the transport of substances across biological membranes (see chapters by Hans H. Ussing and Arthur K. Solomon). There ensued a period of intense activity in a broad range of subjects bearing on membrane transport in physiology. Rather than trace in detail the histories of development of these lines of research, many of which are addressed in subsequent chapters, I describe briefly my current picture of membrane transport in physiology drawn from the results of studies performed by many investigators over several decades.