Fluid production by in vitro lungs from near-term fetal guinea pigs: effects of cortisol and aldosterone.

Lungs from near-term fetal guinea pigs (62 +/- 1 days of gestation) were supported in vitro for 3 h and fluid production was determined by a dye dilution method (Blue Dextran 2000). Three groups of control preparations (N = 6 for each group) showed no changes during incubation. However, cortisol or aldosterone placed in the outer saline during the middle hour caused profound reductions in fluid production. Cortisol at 10(-6) or 10(-8) mol/l reduced production 80.3 +/- 10.8% and 47.8 +/- 20.5%, respectively (p < 0.05-0.001; N = 6 for each group); at 10(-10) mol/l it failed to affect production significantly. Aldosterone was effective at lower concentrations (N = 12). At 10(-11) mol/l it reduced production 67.1 +/- 10.0% (p < 0.01-0.001); at 7 x 10(-10) mol/l it produced similar effects. In contrast, there were no significant changes after treatment with 10(-11) mol/l aldosterone together with an aldosterone antagonist (5 x 10(-8) mol/l spironolactone; N = 6). Spironolactone alone was without effect (N = 6). The highest steroid concentrations tested corresponded to plasma concentrations in the guinea pig at delivery; therefore, it is suggested that both steroids may have a role in reducing lung fluid production close to birth in this species.