Effect of Tocolytics on Surfactant Secretion When Administered with Betamethasone: An in Vitro Study

To analyze the amount of surfactant protein (SP)-B and lecithin/sphingomyelin (L/S) ratio in response to betamethasone (BMS) alone as compared with magnesium sulfate (Mg(2+)), indomethacin (Indo), and nifedipine (Nif) with or without BMS.

NCI-H441 human lung cells were grown and distributed into eight plates. BMS and tocolytics were added and the final plates were: control, BMS only, and each tocolytic ± BMS. Cells were stained with SP-B antibodies and relative fluorescence was measured. Lipids were also extracted, identified, and examined for relative densities. The L/S ratio was calculated.

Nine independent measurements were obtained for each plate. The protein analysis revealed that among all eight plates, SP-B levels were highest among BMS only. There was a nonsignificant decrease in SP-B in each of the combinations of tocolytics + BMS as compared with BMS only. Compared with BMS only, L/S ratio was decreased in Mg(2+) + BMS (p = 0.041), Indo + BMS (p = 0.042), and Nif + BMS (p = 0.025).

In our in vitro human lung cell model, SP-B and L/S ratio increased in response to BMS administration alone. The addition of tocolytics to BMS resulted in no increase in L/S ratio and no changes seen in SP-B production compared with BMS alone.