Biological transport

Abstract

What a strange field is transport! Here the investigator gathers information from kidney tubules, tumor cells, frog skins, gut sacs, and toad bladders. With such as these he observes behavior that violates the intuition of the enzymologist, morphologist, and chemist, and observes the behavior of molecules that may have proved inert in his every other test. Biological transport is by no means a new subject, but it is one that has gained tremendously in interest from the various biological sciences in the last few years. The subject evolved from two rather discrete interests-that of permeability phenomena, extending back more than 60 years, and that of problems of secretion. The difficulties posed by the latter were found in the late 1930s to be associated with the former. With the closer approach to the interpretation of other cellular phenomena, the need to understand how substances and reactions are segregated and brought together in the cell and in the organism has become so pressing that many ingenious, indirect approaches to these questions have been discovered. Meanwhile, the search for the means to identify directly the structures producing transport has continued. This presentation grew from a short series of lectures to an advanced biochemistry class, attended also by graduate students of pharmacology, physiology, microbiology, genetics, and other sciences. It should be interpreted more as a bibliographed syllabus for that instruction than as a review. Accordingly, the author has PREFACE selected the illustrative material and examples that seemed most suitable and familiar to him. The result can hardly seem to have the ideal balance to all the scientific areas now interested in transport. Perhaps physiologists and pharmacologists would like to read more about the intricacies of ion transport, the physical and mathematical biologists more of the theoretical background, the cytolooists more about the morphological substratum, and so on. Although all divergent needs cannot be met, I trust this summary will prove useful to both teaching and learning in various disciplines.

5‐hydroxytryptamine and Dopamine Transport by Rat and Human Blood Platelets

“…Our observation that the V'max value for 5-HT transport by rat platelets was about 5-fold higher than that for dopamine might seem at first sight to be inconsistent with the concept that the two amines are transported by the same process; however, a common (Christensen, 1975). For example, Shaskan & Snyder (1970) found substantial differences in the Vmax values for 5-HT and noradrenaline uptake (via the same carrier) into catecholaminergic neurones.…”

Specificity of neutral amino acid uptake at the basolateral side of the epithelium in the cat salivary gland in situ.

“…The present studies were directed to the identification of neutral amino acid transport systems in the salivary gland, in vivo, which may be compared with carriers widely represented in different animal cells (for reviews see Christensen, 1975;Lerner, 1978).…”

Glycine Transport by Human Diploid Fibroblasts—Absence of a Defect in Cells from Patients with Nonketotic Hyperglycinemia

“…In mammalian cells neutral amino acids have been shown to be transported by at least three different systems, the A, ASC, and L systems (2,5,21,22), which were distinguished by patterns of competitive inhibition (1, 17,18,21,22). The amino acid analog a-aminoisobutyric acid (AIB), a-methylaminoisobutyric acid (MeAIB), and P-2-aminobicyclo(2,2, 1)heptane-2-carboxylic acid (BCH) have been shown to be specific competitive inhibitors of the A, ASC, and L transport systems, respectively (4,6,21).…”