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

Abstract

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× 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 × 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.