“…8,27 (2) Immunoreactive ET-1 is present in amniotic fluid. [28][29][30][31][32] (3) Prepro-ET-1 mRNA is pre sent in, and immunoreactive ET-1 is produced by, avascular human amnion tissue and amnion epithelial cells maintained in monolayer culture. 33,34 The phys iologic and pathophysiologic role of ET-1 formed in amnion is not known but potentially could evolve about the potency of this peptide in evoking smooth muscle contraction.…”