alpha -Adrenoreceptor influences on liquid movements by in vitro lungs from fetal guinea pigs

Departments of Obstetrics and Gynecology and Zoology, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Z4 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 · h 1 · kg body wt 1 , but epinephrine at concentrations known at delivery (10 8 and 10 7 M) produced significant reductions or fluid reabsorption (analysis of variance, regression analysis); at high levels (10 6 and 10 5 M), epinephrine had no effect. Maximal responses from 10 7 M epinephrine involved -adrenoreceptors, since they were abolished by 10 6 M phentolamine ( -antagonist) but were unaffected by 10 6 M propranolol ( -antagonist; n = 36). Activation was through 2 -adrenoreceptors, since responses were abolished by 10 4 M yohimbine ( 2 -antagonist; n = 24) but were resistant to 10 5 M prazosin ( 1 -antagonist; n = 24). At high levels of epinephrine (10 5 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. epinephrine; prazosin; yohimbine; lung fluid The Journal of Applied Physiology 84(2):746-753 8750-7587/98 $5.00 Copyright © 1998 the American Physiological Society