CASR and Hypercalcemia: To test directly the hypothesis that fetal hypercalcemia, acting on the CaSR, provides a physiological stimulus for lung fluid secretion, we cultured E12.5 mouse lungs for 48 hours in medium containing either 1.05 mM or 1.70 mM Ca2+o in presence or absence of Inh-172 (10 μM), before measurements of transepithelial PD were conducted.