Effect of estradiol and progesterone on the isometric tension developed by longitudinal and circular isthmus of rabbit fallopian tube.

The effect of estradiol and progesterone on the isometric tension developed by longitudinal and circular muscle of isthmus of rabbit fallopian tube to various agonists was studied. The isometric tension developed was reduced by about 50% under progesterone dominance as compared to estrogen dominance. This inhibition was of non-specific nature and did not involve adrenergic receptors. The non-specific effect of progesterone may have a role in regulating the entry of ova into the isthmus after their initial retention at the ampullary--isthmic junction.