19(R)-hydroxy PGE1 is the major prostaglandin found in the semen of primates, including man. It is an agonist for the EP1 and EP3 receptor subtypes, and exhibits contractile activity on smooth muscle preparations. It has an EC50 of 320 nM for contracting guinea pig ileum, which express EP1 receptors, and an EC50 of 80 nM for contracting chick ileum, which express EP3 receptors.
