Characterization of thromboxane A2/prostaglandin H2 receptors and histamine H1 receptors in cultured guinea-pig tracheal smooth-muscle cells.
We characterized thromboxane A2/prostaglandin H2 (TXA2/PGH2) receptors and histamine H1 receptors in Guinea-pig cultured tracheal smooth-muscle cells (TSMC). [3H]SQ 29,548 (a TXA2 antagonist)-binding sites were saturable and a high affinity with a dissociation constant of 6.2 +/- 0.60 nM (mean +/- S.E.) and a receptor density of 46 +/- 4.6 fmol/10(6) cells. [3H]SQ 29548 binding was completely inhibited by TXA2 mimetics or antagonists. Intracellular calcium concentration ([Ca2+]i) in TSMC was increased with U46619 stimulation and the increase was attenuated by TXA2 antagonists, the potencies of which correlated with those inhibiting the activities of the [3H]SQ 29548 binding. [3H]Mepyramine (a H1 antagonist)-binding sites were also present in TSMC. [3H]Mepyramine had a single class of low-affinity-binding sites with a dissociation constant of 2.6 +/- 0.081 microM and a receptor density of 10.6 +/- 0.11 nmol/mg protein. [3H]Mepyramine binding in TSMC membrane was inhibited by H1 antagonists, but not by H2 antagonists. The inhibition constants of mepyramine in TSMC were 910-times lower than those in tracheal membranes. In contrast, the histamine-induced increase in [Ca2+]i in TSMC was inhibited in the presence of low concentrations of H1 antagonists. All these observations provide evidence that TXA2/PGH2 receptors, mepyramine-binding sites and/or H1 receptors are expressed in cultured TSMC.
Pharmaceutical Research Laboratories, Kyowa Hakko Kogyo Co., Ltd., Shizuoka, Japan.
I
I
Miki
H
H
Nonaka
A
A
Ishii
D000818:Animals; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D005231:Fatty Acids, Unsaturated; D006168:Guinea Pigs; D006634:Histamine H1 Antagonists / Q000378:metabolism / Q000494:pharmacology; D006834:Hydrazines / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D011450:Prostaglandin Endoperoxides, Synthetic / Q000494:pharmacology; D011463:Prostaglandins H / Q000378:metabolism*; D011738:Pyrilamine / Q000378:metabolism / Q000494:pharmacology; D011969:Receptors, Histamine H1 / Q000378:metabolism*; D011982:Receptors, Prostaglandin / Q000378:metabolism*; D017482:Receptors, Thromboxane / Q000037:antagonists & inhibitors / Q000378:metabolism*; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D014132:Trachea / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*
D019086:Bridged Bicyclo Compounds, Heterocyclic; D005231:Fatty Acids, Unsaturated; D006634:Histamine H1 Antagonists; D006834:Hydrazines; D011450:Prostaglandin Endoperoxides, Synthetic; D011463:Prostaglandins H; D011969:Receptors, Histamine H1; D011982:Receptors, Prostaglandin; D017482:Receptors, Thromboxane; D044244:Receptors, Thromboxane A2, Prostaglandin H2; C045749:SQ 29548; D011738:Pyrilamine; D002118:Calcium