[3H]Adenosine binding to rat mast cells--pharmacologic and functional characterization.

Rat serosal mast cell adenosine receptors were characterized by [3H]adenosine binding to cell membrane particulates, and functional changes in mast cell mediator release and cyclic AMP levels were assessed, utilizing various adenosine analogs. [3H]adenosine binding to sonicated mast cell membrane preparations at 0 degrees C in the presence of deoxycoformycin is linear with initial cell number, rapid and reversible. The cells display 16,400 +/- 1600 high affinity [3H]adenosine binding sites/cell, equivalent to 118 fmol bound/mg protein, with an equilibrium dissociation constant of 27.97 +/- 3.0 nM. Competition studies reveal that adenosine greater than 2-chloroadenosine greater than NECA greater than L-PIA greater than D-PIA in competing for [3H]adenosine binding sites and that aminophylline and cromolyn sodium also bind to the putative receptor. Adenosine and its analogs, NECA, and L-PIA, appear to activate adenylate cyclase in resting mast cells by raising cyclic AMP, suggesting an Ra cell surface adenosine receptor subtype; these same analogs potentiate mast cell B-hexosaminidase release stimulated by specific antigen. The identification of rat mast cell [3H]adenosine binding sites whose stimulation augments resting cell cyclic AMP levels and antigen-induced mediator release suggests that these receptors may be important in the biochemical mechanisms of allergic diseases. The ability to assess the number and affinity of mast cell adenosine receptors will enable one to monitor receptor alterations during pharmacologic manipulation and in disease states.