Doe, S., and A. M. Perks. -Adrenoreceptor influences on liquid movements by in vitro lungs from fetal guinea pigs. J. Appl. Physiol. 84(2): 746-753, 1998.Lungs from near-term fetal guinea pigs (60 ± 2 days of gestation) were supported in vitro for 3 h; lung liquid production was monitored by a dye-dilution method. Studies of 30 fetuses showed that untreated preparations produced fluid at 1.34 ± 0.21 ml · h¹ · kg body wt¹, but epinephrine at concentrations known at delivery (10⁸ and 10⁷ M) produced significant reductions or fluid reabsorption (analysis of variance, regression analysis); at high levels (10⁶ and 10⁵ M), epinephrine had no effect. Maximal responses from 10⁷ M epinephrine involved -adrenoreceptors, since they were abolished by 10⁶ M phentolamine (-antagonist) but were unaffected by 10⁶ M propranolol (-antagonist; n = 36). Activation was through ₂-adrenoreceptors, since responses were abolished by 10⁴ M yohimbine (₂-antagonist; n = 24) but were resistant to 10⁵ M prazosin (₁-antagonist; n = 24). At high levels of epinephrine (10⁵ M), where responses did not normally occur, reductions in lung liquid production were large if prazosin was also present (n = 24), and increases were significant if yohimbine was included (n = 24). In guinea pigs, epinephrine appears to activate lung fluid reabsorption through ₂-adrenoreceptors; at high concentrations only, it can also increase production through ₁-adrenoreceptors. Therefore, species differences appear to exist.