The effects of bumetanide and furosemide on lung liquid secretion in fetal sheep.

Thirty-four experiments were carried out on the effects of loop diuretics on lung liquid secretion in 20 fetal sheep (128-145 days gestation) with indwelling catheters. Bumetanide placed in the lung liquid at 2.19 +/- 0.52 X 10(-4) M produced immediate reabsorption of fluid, and effects lasted 3 hr (n = 6). Bumetanide at 1.1 +/- 0.17 X 10(-5) M reduced secretion significantly for 2 hr (n = 4), but at 1.07 +/- 0.06 X 10(-6) M there was no clear effect (n = 6). Controls showed no significant change (n = 6). Furosemide was less effective. At 3.1 +/- 0.07 X 10(-3) M it produced an immediate reabsorption, which lasted 3 hr, but at 1.0 +/- 0.04 X 10(-4) M it increased secretion slightly (n = 4); controls showed no significant change (n = 6). The results are consistent with the presence of a chloride transport system, perhaps with sodium cotransport, as the major factor in fetal lung liquid secretion.