Hisako Yamagishi1,2,*, Masahito Watanabe1,3, Kinya
Yazaki1,2, Kohei Sawaki1,2 and Mitsuru Kawaguchi1,2
Department╩of Pharmacology and 2Oral Health Science Center, Tokyo Dental College,
1-2-2 Masago, Mihamaku, Chiba 261-8502, Japan
3Environment╩& Safety Research Department, Research & Development Division,
Nihon Bayer Agrochem K.K., Yuki Research Center, 9511-4, Yuki, Yuki-shi, Ibaraki 307-0001, Japan
*╩To whom correspondence should be addressed(1).
Abstract: Pharmacological characterization of peripheral type benzodiazepine receptors in rat, rabbit, mouse and human salivary glands was determined by receptor binding and photoaffinity labeling analysis using [3H]PK14105 (1-(2-fluoro-5-nitrophenyl)-3-isoquinolinecarboxylic acid). [3H]PK14105 bound to the membranes of salivary glands in rats, rabbits, mice and humans with high affinity at the nanomolar level. The rank order of receptor density in submandibular glands among several species was as follows: human╩³╩rat╩³╩mouse>╩rabbit. Competitive potency of receptor ligands against [3H]PK14105 was as follows: PK11195╩³╩Ro5-4864>╩diazepam╩>╩clonazepam╩>╩Ro15-1788. The rank order of potency against calcium channel ligands and co-transport inhibitors was as follows: nitrendipine╩>╩BAY╩K╩8644╩>╩bumetanide╩>╩furosemide. Pretreatment with nitrendipine or BAY╩K╩8644 decreased the affinity of [3H]PK14105 binding to rat parotid gland membranes, without changing the density. The photoaffinity labeling with [3H]PK14105 indicated the presence of the 18-kDa protein in all salivary glands of our experiment. The inhibition of photolabeling by some receptor ligands was the same results as the receptor binding assay. In conclusion, the peripheral type benzodiazepine receptors include the 18-kDa protein photolabeled with [3H]PK14105 in salivary glands of rat, mouse, rabbit and human.
Keywords: Peripheral type benzodiazepine receptor, Salivary gland, Photoaffinity labeling, [3H]PK14105