Characterization of histamine H1 and H2 receptors in the rabbit isolated ovarian artery and vein.

Histamine H1 and H2 receptors in the rabbit isolated ovarian artery and vein were studied. Histamine (10(-6)-3 X 10(-4) M) and 2-thiazolylethylamine (2ThEA) (10(-5)-3 X 10(-4)) concentration dependently caused contraction of both vessels. The -log EC50 for the artery was 5.20 +/- 0.13 and 4.48 +/- 0.01, and for the vein it was, 5.50 +/- 0.10 and 5.10 +/- 0.27, respectively. Metiamide (10(-5) M) significantly potentiated histamine-induced but not 2ThEA-induced contractions. The pA2 for antagonism by mepyramine against histamine and 2ThEA was 8.80 +/- 0.20 (slope = 0.73) and 9.02 +/- 0.11 (slope = 0.74) in the artery and 9.50 +/- 0.30 (slope = 1.0 +/- 0.2) and 9.00 +/- 0.20 (slope = 1.0 +/- 0.1) in the vein. Histamine and impromidine concentration dependently relaxed the contracted ovarian artery and vein. Impromidine was 300-fold and sixfold more potent than histamine in the artery and vein, respectively. The relaxant potency of histamine was the same in both vessels. The relaxations were antagonized by metiamide (10(-5) M). The KB against histamine and impromidine was similar in both vessels. These results indicate that functional histamine H1 and H2 receptors exist in the ovarian artery and vein. The possible relevance of this to the proposed role of histamine in ovulation is discussed.