Molecular Pharmacology, Vol 15, 28-34, Copyright © 1979 by the American Society for Pharmacology and Experimental Therapeutics

Identification of Muscarinic Binding Sites in Human Neutrophils by Direct Binding

¹ Department of Chemistry, University of Colorado, Boulder, Colorado 80309

Using techniques developed for the study of muscarinic cholinergic receptors in brain homogenate, direct binding to whole live neutrophils has been shown for the potent muscarinic antagonist [³H]quinuclidinyl-benzilate. The specific binding is saturable, proportional to cell concentration, and can be displaced by atropine, oxotremorine, and piocarpine. The K_d for this system is approximately 8 nM. This whole-cell binding correlates with previously reported effects of cholinergic agents on neutrophil guanosine cyclic 3',5'-monophosphate levels, chemotaxis, and lysosomal enzyme release. Quinuclidinyl-benzilate is shown here to function as a muscarinic antagonist in neutrophils by blocking the carbachol stimulated lysosomal enzyme release in vitro from live cells.

Note:
ACKNOWLEDGMENTS We wish to thank Ms. Nannette A. Schwartzman from Dr. Peter Henson’s laboratory for invaluable discussion of lysosomal enzyme release techniques.