Effects of lung expansion on lung liquid production in vitro by lungs from fetal guinea-pigs. II. Evidence for generation of an inhibitory factor.
Lungs from near-term fetal guinea-pigs were supported in vitro for 3 h; lung liquid production was measured by a dye-dilution method using Blue Dextran 2000 [fetuses 63 +/- 2 days of gestation, 97.6 +/- 19.8 (SD) g body weight]. Preparations were incubated in pairs taken from the same mother. Twenty lungs incubated in pairs without treatment (controls) showed no significant changes in fluid production throughout incubation (analysis of variance; regression analysis); rates in successive hours were: first lung, 1.36 +/- 0.39, 1.09 +/- 0.34 and 1.27 +/- 0.42 ml/kg body weight per h; second lung, 1.46 +/- 0.52, 1.09 +/- 0.41 and 1.18 +/- 0.43 ml/kg body weight per h. Twenty lungs were incubated similarly in pairs, but after one hour one lung from each pair was expanded with Krebs-Henseleit saline in volumes approximating those of the first breath (68 +/- 10% of lung volume). The expanded lungs began to reabsorb fluid immediately after expansion; the untreated lungs also stopped production or reached reabsorption by the final hour. Rates in successive hours were: expanded lungs; before expansion, 1.00 +/- 0.21, after expansion, -0.23 +/- 0.17 and 0.14 +/- 0.09 ml/kg body weight per h; unexpanded lungs, 1.27 +/- 0.49, 0.02 +/- 0.01 and -0.01 +/- 0.004 ml/kg body weight per h. The decrease in production was significant for each type of lung. The effects persisted in both expanded and unexpanded lungs in the presence of 1.78 x 10(-5) M phentolamine (n = 12; 70 +/- 2% expansion). The results suggest that expansion of the lungs at birth may release an unknown inhibitory factor, provisionally termed Expansion Factor (EF), within the lungs; this agent, probably not a catecholamine, can change lung fluid production into reabsorption and may partly account for the failure of beta-antagonists to prevent fluid reabsorption at delivery.
Nelson
P G
PG
Department of Zoology, University of British Columbia, Vancouver, Canada.
Perks
A M
AM
D000042:Absorption / Q000187:drug effects / Q000502:physiology; D000704:Analysis of Variance; D000818:Animals; D001685:Biological Factors / Q000502:physiology*; D001826:Body Fluids / Q000378:metabolism*; D002395:Catecholamines / Q000037:antagonists & inhibitors; D005314:Embryonic and Fetal Development / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D008168:Lung / Q000187:drug effects / Q000196:embryology / Q000378:metabolism*; D008176:Lung Volume Measurements; D010646:Phentolamine / Q000494:pharmacology; D012044:Regression Analysis
D001685:Biological Factors; D002395:Catecholamines; D010646:Phentolamine