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EFFECT OF CALCIUM WITHDRAWAL AND AGENTS AFFECTING CALCIUM TRANSLOCATION ON AGONIST‐INDUCED CONTRACTIONS OF THE RABBIT OVARIAN ARTERY
Author(s) -
Oriowo M. A.,
Bevan J. A.
Publication year - 1986
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1986.tb02384.x
Subject(s) - histamine , calcium , diltiazem , medicine , endocrinology , extracellular , chemistry , egta , contraction (grammar) , antagonist , calcium in biology , biology , receptor , biochemistry
SUMMARY 1. The effect of extracellular calcium ion (Ca 2+ ) depletion, diltiazem, D‐600 and TMB‐8 on potassium (K + ), norepinephrine‐(NE) and histamine‐induced contractions of the rabbit isolated ovarian artery was studied. 2. K + ‐induced contractions, which were biphasic, were rapidly lost (∼ 5 min) when calcium was removed from the physiological saline solution (O‐Ca 2+ PSS). NE and histamine‐induced contractions also declined rapidly under nominal O‐Ca 2+ conditions without any evidence of a depletion resistant component. However, after 1 h under these conditions there was a partial restoration of their responses. 3. EGTA (10 ‐3 mol/l) abolished these contractions to NE and histamine but not those in normal PSS. 4. Diltiazem and D‐600 were more effective against K + ‐induced than NE‐ and histamine‐induced contractions while the intracellular Ca 2+ antagonist TMB‐8 was equally effective against all three responses. 5. Histamine could still evoke contraction of the K + ‐contracted ovarian artery after this had been completely abolished with diltiazem or D‐600 but not TMB‐8. 6. These results are interpreted to suggest that K + , NE and histamine probably release intracellular Ca 2+ to evoke contractions of the ovarian artery. They differ, however, in the mechanisms they employ to facilitate entry of extracellular calcium, which in turn leads to intracellular calcium release.