Prostaglandin synthesis by human amnion is dependent upon extracellular calcium

Prostaglandin (PG) E and F output was studied in collagenase-dispersed amnion cells to determine the effect of extracellular Ca2+ upon PG synthesis. In the presence of 2.5 mM CaCl2, PGE and PGF output (picograms per 10(5) cells per 3 h) by cells obtained at term prior to labour following elective cesarean section (CS) was 183 +/- 39 and 127 +/- 23, respectively. This increased to 435 +/- 111 (p less than 0.025) and 241 +/- 49 (p = 0.056) from cells obtained after spontaneous labour and delivery at term (SL). Exclusion of CaCl2 from the medium (plus 0.1 mM EGTA) significantly reduced (p less than 0.025) PGE output in CS and SL cells (83 +/- 22 and 183 +/- 47, respectively) and PGF output in CS cells (70 +/- 17). PGE output in both CS and SL cells was unchanged when CaCl2 concentrations in the medium were decreased from 2.5 to 0.25 mM, but significantly attenuated (p less than 0.01) when extracellular CaCl2 was decreased from 0.25 to 0 mM. The voltage-sensitive Ca2+ channel blocker, D-600, decreased PGE output in the presence of (2.5 mM) CaCl2 to levels observed in the absence of CaCl2. Ionophore A23187 restored PGE output in the presence of D-600 and Ca2+. PGE output from CS amnion cells was stimulated by A23187 and elevated extracellular K+ (40 mM). In each case, exclusion of CaCl2 from the medium eliminated the response. These results suggest that PG output by human amnion is dependent, in part, upon the presence of extracellular Ca2+ and that Ca2+ may enter the cell via a potential-sensitive mechanism.