Prostaglandin and leukotriene receptors in pulmonary, vascular, and uterine smooth muscle

Prostaglandins are currently used to maintain patency of the ductus arteriosus and to elicit uterine contractions. Prostaglandin synthesis inhibitors are used to promote closure of the ductus and their administration in pregnant animals has produced fetal pulmonary hypertension. Exposure of the human fetus to inhibitors of prostaglandin synthesis has been associated with persistent pulmonary hypertension. A case report of a child with primary hypertension supports the hypothesis that the balance of prostaglandin metabolites plays an important role in maintaining PVR. Leukotrienes have been identified in the sputum of allergic asthmatic patients, patients with cystic fibrosis and infants with persistent pulmonary hypertension. Leukotriene inhibition in rats and newborn lambs prevented and reversed HPV. Receptors for prostaglandins have been identified in smooth muscle preparations of the uterus and renal glomerulus. Further studies have characterized the binding sites in lung tissue, giving supportive evidence for the existence of receptor sites there. Specific receptor sites for LTC4 and LTD4 have been demonstrated in lung tissue. Temperature, pH, and the presence of cations and guanine nucleotides have been shown to affect the receptor density and affinity. Lewis et al demonstrated that the characteristics of the receptor for [3H]LTD4 in the human lung are identical in adult and fetal tissue. This leads to the need for further investigation of the receptors and the effects of the local environments in an attempt to explain the physiologic changes seen in the successful and unsuccessful transition from fetal to neonatal circulation.