Biochemical Studies of Taste Sensation V. Binding of Quinine to Bovine Taste Papillae and Taste Bud Cells

Abstract

Quinine tastes bitter to humans and is rejected by cows in taste tests. In this study quinine was used as a ligand in binding experiments with various types of preparation of taste and non-taste tissues from bovine tongue using fluorescence to quantitate quinine binding. Studies were carried out attempting to demonstrate binding specificity of the ligand using taste papillae in situ, those excised from the tongue, homogenates of entire papillae, homogenates of epidermis of circumvallate papillae, and isolated taste cell suspensions; in each experiment, comparable control tongue tissue devoid of taste buds was included.

Binding of small quantities of quinine to tissue can be reliably determined. In general, however, there is as much binding to non-taste preparations as occurs to those which contain taste buds. In contrast to earlier experiments involving taste stimulus molecules for which specific binding could be demonstrated, the present experiments using quinine show that the hypothesis of peripheral specificity in binding for this bitter tasting ligand is not supported.

The results demonstrated that although binding of quinine to taste tissue can be quantitated, measurement of binding per se is not a sufficient indicator of taste specificity in this case. At the present level of analysis, however, the data do not exclude the possibilities either that specificity determination in quality recognition for bitter may lie subsequent to the initial binding of quinine, or that specificity may be a property of the relative orientation of the stimulus molecule at the receptor membrane.

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Notes on contributors

Robert H. Cagan

Joyce Laing works in the Department of Child and Family Psychiatry, Playfield House, Cupar, Fife, and is a Consultant Art Therapist to Psychiatric Hospitals and Prisons and Chairwoman of the Scottish Society of Art and Psychology.