Taste Tissue Research Articles

Biochemical studies of taste sensation: binding to taste tissue of 3H-labeled monellin, a sweet-tasting protein.

Binding of 3H-labeled methylated monellin to taste receptor tissue was demonstrated in vitro. Preparation of bovine and human circumvallate (taste) papillae bound more of the ligand than did lingual and nonlingual epithelial preparations devoid of taste buds. Binding to the taste preparations saturated at high ligand concentrations. Furthermore, sugars and other sweet-tasting molecules appeared to compete to some extent with this sweet-tasting protein for its binding sites. These binding measurements of the intensity sweet-tasting protein monellin to taste receptor preparations help to establish the binding interactions as an initial step taste sensation.

Biochemical studies of taste sensation. V. Binding of quinine to bovine taste papillae and taste bud cells.

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.

The plasma membranes of bovine circumvallate papillae isolation and partial characterization

1. 1. A procedure has been established to isolate plasma membranes and other subcellular membranes from bovine circumvallate papillae by means of discontinuous sucrose density gradient centrifugation. From bovine circumvallate, which is the papilla that contains the most taste buds, about 240 μg plasma membrane proteins per g tissue, or 3.1 μg membrane protein per mg homogenate protein, was obtained. 2. 2. Electron microscopy and marker enzyme studies confirmed the purity of th membrane fractions. Among the cellular membranes, the plasma membranes have the highest specific activities of ouabain-sensitive (Na +K +Mg 2+)-ATPase (EC 3.6.1.4) and 5′-nucleotidase (EC 3.1.3.5). 3. 3. [ 14C]Fructose was found to bind preferentially to the taste papillae plasma membranes when mixed with the particulare fraction of the whole homogenate. The [ 14C]fructose-bound plasma membranes could be subsequently isolated by sucrose density gradient centrifugation. On the other hand, plasma membranes from mount papillae which contain no taste buds failed to show such preferential binding with the taste stimulant fructose. 4. 4. The preferential binding of 14C-labeled fructose to the plasma membranes of circumvallate papillae suggests that taste receptors of taste tissues may be located in the plasma membranes.