Critique of current views on receptors, and a new general theory of receptor location and action in vivo.
The Davson-Danielli model of the cell membrane accounted for nearly all the space within it by suggesting that it was composed of structural proteins and lipids; this would leave virtually no space for the large number of enzymes, carriers, antigens, antibodies, and receptors for hormones, transmitters, drugs and toxins, generally believed to be present within the membranes. The sizes of many of the structural proteins, lipids, enzymes and receptors, have been measured by electron microscopic techniques, and are too large to be located within or next to the Robertson 'unit' membrane or the Singer-Nicolson membrane, without producing bulges; these are never seen by transmission electron microscopy, and rarely by freezing techniques. If they were present but unstained, gaps should appear in the membranes corresponding to the measured dimensions of these macromolecules; such gaps are not seen. It has been assumed that the substances react with receptors located only at the cell membrane, but, in the intact organism, they pass through many cellular phases before having any effect; one hundred and five phases in the passage from the blood to the brain are identified. It is suggested that the receptor is the sum total of all the reactions between the substances added and each of the phase reacting to a differing degree. Experiments which could assess the relative validity of the currently accepted and new ones proposed are listed.
Hillman
H
H
Unity Laboratory of Applied Neurobiology, University of Surrey, Guildford, England.
D000818:Animals; D001693:Biological Transport, Active; D002462:Cell Membrane / Q000648:ultrastructure*; D006801:Humans; D008854:Microscopy, Electron; D008954:Models, Biological; D011956:Receptors, Cell Surface
D011956:Receptors, Cell Surface