Premium
Histamine mediates the muscle layer‐specific responses in the isolated swine myometrium
Author(s) -
KITAZAWA T.,
SHISHIDO H.,
SATO T.,
TANEIKE T.
Publication year - 1997
Publication title -
journal of veterinary pharmacology and therapeutics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.527
H-Index - 60
eISSN - 1365-2885
pISSN - 0140-7783
DOI - 10.1111/j.1365-2885.1997.tb00094.x
Subject(s) - pyrilamine , histamine , myometrium , mepyramine , histamine h1 receptor , chemistry , medicine , contraction (grammar) , endocrinology , muscle contraction , biophysics , biology , receptor , biochemistry , antagonist , uterus
To clarify the role of histamine in uterine contractility, the effect of this biogenic amine on the myometrium of cyclic mature gilts was investigated by an isometric tension recording study in vitro . In addition, using crude membrane preparations isolated from the longitudinal (LM) and circular muscle (CM), the distribution of H1 histamine receptors was characterized by 3 H‐pyrilamine binding assay. Histamine caused a tetrodotoxin‐resistant contractile response of LM and CM in Krebs solution, but LM (‐logEC 50 = 6.34) was more sensitive than CM (‐logEC 50 = 5.4). Pyrilamine decreased the excitatory response of histamine in both muscle layers. In pyrilamine‐treated LM, a high concentration of histamine (1‐30 μm) caused a slight inhibition of spontaneous contraction, and this inhibition was abolished by ranitidine. On the other hand, histamine did not cause any inhibition in the pyrilamine‐treated CM preparations. Dimaprit (10‐300 μm) concentration‐dependently inhibited the spontaneous contraction of LM but not of CM. In the presence of pyrilamine and ranitidine, N α‐methylhistamine, even at 10 μm, did not affect the spontaneous and electrical field stimulation (5Hz)‐induced contraction of LM and CM layers. Specific 3 H‐pyrilamine binding sites were distributed heterogeneously in the swine myometrium. The maximum number of binding sites in LM (132.5 ± 9.9 fmol/mg protein, n = 10) was 2.5 times higher than that in CM (52.2 ± 3.2 fmol/mg protein, n = 6). These results indicate that there is a muscle layer‐dependent difference of histamine‐induced response in the swine myometrium. In the LM layer, histamine acts on both H1 and H2 histamine receptors, and causes contraction (via H1 receptors at a low concentration) or relaxation (via H2 receptors at a high concentration in the presence of pyrilamine). However, histamine causes only a contraction in the CM layer, likely the result of the absence of H2 histamine receptors. Histamine‐induced contraction is conspicuous in the LM layer, because of the heterogeneous distribution of H1‐receptors between LM and CM.