Effects of cAMP, its analogues, and forskolin on lung fluid production by in vitro lung preparations from fetal guinea pigs

1992 ◽  
Vol 70 (3) ◽  
pp. 330-337 ◽  
Author(s):  
Pawel M. Kindler ◽  
Sepideh Ziabakhsh ◽  
Anthony M. Perks
Keyword(s):  
Guinea Pigs ◽  
Fetal Lung ◽  
Dilution Method ◽  
Adenylate Cyclase System ◽  
Dibutyryl Camp ◽  
Lung Fluid ◽  
Fluid Production ◽  
High Doses ◽  
Lung Liquid

Lungs from 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, based on Blue Dextran 2000. Twenty untreated lungs produced fluid at 1.41 ± 0.22 mL∙kg−1 body weight∙h−1, with no significant changes during later hours. Treatments with analogues of cAMP, cAMP, or forskolin during the middle hour reduced production significantly. Dibutyryl cAMP at 10−3 M produced reabsorption (117.8 ± 13.6% reduction, p < 0.001, n = 10); at 10−4 M it reduced production (77.3 ± 11.0% fall, p < 0.001, n = 10). 8-Bromo-cAMP appeared more effective; at 10−4 M it caused slight reabsorption (109.0 ± 8.9% reduction, p < 0.001, n = 6) and at lower concentrations it decreased production (at 10−6 M, 67.6 ± 9.6% fall, p < 0.001, n = 6; at 10−7 M, 40.0 ± 14.3% fall, p < 0.001, n = 6). At high doses, cAMP itself produced similar effects (at 5 × 10−3 M, 141.6 ± 22.8% reduction, p < 0.001, n = 6); at 10−4 it was ineffective (n = 3). Forskolin at 10−6 M induced the strongest reabsorptions seen (159.1 ± 10.9% reduction, p < 0.001, n = 6); at lower concentrations it reduced production (at 10−8 M, 73.8 ± 5.5% fall, p < 0.001, n = 6; at 10−9 M, 29.2 ± 9.2% fall, p < 0.05, n = 6). These results suggest a possible role for the adenylate cyclase system in the arrest of lung liquid production in the guinea pig around birth.Key words: cAMP, forskolin, fetal lung, lung fluid.

Effects of lung expansion on lung liquid production in vitro by lungs from fetal guinea-pigs. II. Evidence for generation of an inhibitory factor

1996 ◽  
Vol 8 (3) ◽  
pp. 347 ◽  
Author(s):  
PG Nelson ◽  
AM Perks
Keyword(s):  
Body Weight ◽  
Guinea Pigs ◽  
Inhibitory Factor ◽  
Dilution Method ◽  
Lung Fluid ◽  
Lung Expansion ◽  
Fluid Production ◽  
Near Term ◽  
Lung Liquid

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.

Lung-liquid production in vitro by lungs from fetal guinea pigs: effects of amiloride on responses to aldosterone

1997 ◽  
Vol 75 (7) ◽  
pp. 1147-1154 ◽  
Author(s):  
A. M. Perks ◽  
M. Stockbrocks ◽  
D. C. Chuang ◽  
I. Vonder Muhll ◽  
P. W. Kindler
Keyword(s):  
Regression Analysis ◽  
Guinea Pigs ◽  
Response Curve ◽  
Plasma Concentrations ◽  
Dilution Method ◽  
M 10 ◽  
Fluid Production ◽  
Near Term ◽  
Lung Liquid

Lungs from near-term fetal guinea pigs (62 ± 2 days of gestation) were supported in vitro for 3 h; lung-liquid production was monitored by a dye-dilution method based on Blue Dextran 2000. Untreated preparations produced fluid at 1.26 ± 0.14 mL∙kg−1 body mass∙h−1, with no significant change over the ensuing hours (ANOVA, regression analysis; n = 16). Experimental preparations received aldosterone at plasma concentrations reported to be present at birth. Aldosterone produced rapid, significant reductions in fluid production, and occasionally reabsorptions, which persisted beyond treatment. Reductions during treatment were as follows: 10−8 M aldosterone, 90.8 ± 4.9% (P < 0.001; n = 4); 2 × 10−9 M aldosterone, 64.1 ± 16.6% (P < 0.05–0.001; n = 6), and 7 × 10−10 M aldosterone, 48.6 ± 11.7% (P < 0.005–0.001; n = 6). The linear log dose response curve (r = 0.99) showed a theoretical threshold at 3.4 × 10−11 M aldosterone. Responses to 7 × 10−10 M aldosterone were abolished by 10−6 M amiloride. At the highest concentration of aldosterone (10−8 M), 10−6 M amiloride significantly reduced responses, and the changes were no longer significant by ANOVA. At both high and low aldosterone concentrations, responses with amiloride were significantly lower than those without amiloride (ANOVA, P < 0.03–0.04). Amiloride controls and untreated preparations showed no significant changes in fluid production. It is concluded that aldosterone at plasma concentrations present at birth can cause reductions in lung-liquid production or reabsorption through effects on amiloride-sensitive Na+ channels, and that the responses are remarkably rapid.

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

1998 ◽  
Vol 84 (2) ◽  
pp. 746-753 ◽  
Author(s):  
S. Doe ◽  
A. M. Perks
Keyword(s):  
Regression Analysis ◽  
Guinea Pigs ◽  
Species Differences ◽  
Dilution Method ◽  
Fluid Reabsorption ◽  
Lung Fluid ◽  
Near Term ◽  
High Concentrations ◽  
Lung Liquid

Doe, S., and A. M. Perks. α-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 α-adrenoreceptors, since they were abolished by 10−6 M phentolamine (α-antagonist) but were unaffected by 10−6 M propranolol (β-antagonist; n = 36). Activation was through α2-adrenoreceptors, since responses were abolished by 10−4 M yohimbine (α2-antagonist; n = 24) but were resistant to 10−5 M prazosin (α1-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 α2-adrenoreceptors; at high concentrations only, it can also increase production through α1-adrenoreceptors. Therefore, species differences appear to exist.

Fluid production by in vitro lungs from fetal guinea pigs

1990 ◽  
Vol 68 (4) ◽  
pp. 505-513 ◽  
Author(s):  
A. M. Perks ◽  
J. J. Dore ◽  
R. Dyer ◽  
J. Thom ◽  
J. K. Marshall ◽  
...  
Keyword(s):  
Guinea Pigs ◽  
Average Rate ◽  
Fluid Secretion ◽  
Independent Study ◽  
Fluid Composition ◽  
Lung Fluid ◽  
Fluid Production ◽  
Lung Liquid ◽  
Secretion Rates

Lungs from fetal guinea pigs (54–67 days of gestation) were supported in vitro, and lung liquid secretion rates were measured by a dye-dilution technique. The average secretion rate in the first hour was 2.14 ± 0.08 (SE) mL∙kg−1 body weight∙h−1 (0.21 ± 0.01 mL/h) (n = 450); this was comparable to intact preparations. In an independent study of 30 lungs, secretion continued unchanged for 3 h, with no significant change in fluid composition. Between 54 days and term, production appeared to fall in terms of millilitres per kilogram per hour. The following agents were placed in the supporting saline during the middle hour of incubation. (i) Sodium iodoacetate: at 10−4 M this produced a fall in secretion (fall, succeeding hours; 55.4 ± 23.0 and 64.9 ± 17.5%; n = 6); at 10−3 M it stopped secretion (fall, succeeding hours; 87.2 ± 10.3 and 100%, n = 6). (ii) Ouabain: at 10−5 M there was no change in production (n = 6); at 10−4 M, four preparations were unaffected, two reduced production. (iii) Epinephrine (10−7 M) produced a significant fall in production in all cases (n = 6); in four preparations secretion reduced (average fall, 64.4 ± 10.8%); in two preparations there was reabsorption (average rate, −1.03 mL∙kg−1∙h−1). This extends the effect of epinephrine to the guinea pig, and suggests that the in vitro preparation is a useful model for studies of the fetal lung.Key words: fetus, lung fluid, secretion, iodoacetate, epinephrine.

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

1993 ◽  
Vol 129 (2) ◽  
pp. 169-177 ◽  
Author(s):  
Pawel M Kindler ◽  
Deuel C Chuang ◽  
Anthony M Perks
Keyword(s):  
Guinea Pig ◽  
Guinea Pigs ◽  
Plasma Concentrations ◽  
Dilution Method ◽  
Aldosterone Antagonist ◽  
Blue Dextran ◽  
Lung Fluid ◽  
Fluid Production ◽  
Near Term

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.

The effects of furosemide and bumetanide on lung liquid production by in vitro lungs from fetal guinea pigs

1990 ◽  
Vol 68 (8) ◽  
pp. 1131-1135 ◽  
Author(s):  
J. Thom ◽  
A. M. Perks
Keyword(s):  
Body Weight ◽  
Guinea Pig ◽  
Guinea Pigs ◽  
Loop Diuretics ◽  
Dilution Technique ◽  
Blue Dextran ◽  
Lung Fluid ◽  
Lung Liquid ◽  
Secretion Rates

Lungs from fetal guinea pigs of 61 ± 3 days of gestation were supported in vitro for 3 h, and lung liquid secretion rates were measured by a dye dilution technique based on Blue Dextran 2000. Ten preparations that had received no treatment showed an average secretion rate of 1.12 ± 0.28 mL∙kg−1 body weight∙h−1 during the first hour, and there were no significant changes over the following 2 h. In studies of 54 fetal lungs, furosemide, bumetanide, control ethanol carrier, or saline alone were placed in the supporting medium during the middle hour of the 3-h incubations (ABA design). Furosemide at 10−3 M reduced secretion 83.4 ± 16.8%; at 10−4 and 10−5 M it produced smaller reductions. Bumetanide at 10−3 M usually produced reabsorption (129.9 ± 23.0% reduction), at 10−4 M it reduced secretion 30.9 ± 11.8%, but at 10−5 M it was ineffective. Control carrier and saline were without effect. The ability of the loop diuretics to produce reabsorption of fluid in some preparations suggests the unmasking of an active reabsorptive process. The results also suggest that lung liquid secretion in the fetal guinea pig, as in the sheep, is dependent on a Na+ and Cl− cotransport system.Key words: fetus, lung fluid, bumetanide, furosemide.

Reabsorption of lung liquid produced by 2,4-dinitrophenol in in vitro lungs from fetal guinea pigs

1993 ◽  
Vol 71 (1) ◽  
pp. 1-11 ◽  
Author(s):  
A. M. Perks ◽  
T. Ruiz ◽  
B. Chua ◽  
I. Vonder Muhll ◽  
P. M. Kindler ◽  
...  
Keyword(s):  
Body Weight ◽  
Regression Analysis ◽  
Guinea Pigs ◽  
Dilution Technique ◽  
Dye Dilution ◽  
Fluid Production ◽  
Oxidative Processes ◽  
Near Term ◽  
Lung Liquid

Lungs from near-term fetal guinea pigs (62 ± 2 days of gestation) were supported in vitro for 3 h, and lung liquid production was measured by a dye dilution technique. Twelve untreated preparations produced fluid at 1.54 ± 0.29 mL∙kg−1 body weight∙h−1 during the 1st h, with no significant changes in later hours. Twelve preparations treated with 2 × 10−4 M 2,4-dinitrophenol (DNP) showed strong reabsorptions (significant, ANOVA and regression analysis); total loss of lactate from the preparations doubled (significant, same tests). In 12 additional preparations, increasing DNP fivefold did not abolish reabsorption; results resembled those at the lower concentration. Amiloride at 10−6 M abolished reabsorptions after 2 × 10−4 M DNP, although fluid production still halted (n = 6; reductions significant, same tests). Amiloride alone had no effect (n = 6); untreated controls showed no change (n = 6). Similarly, 10−4 M sodium iodoacetate virtually abolished reabsorptions after 2 × 10−4 M DNP, although fluid production still stopped (n = 6; reductions significant, same tests). Iodoacetate alone only reduced fluid production (n = 6; significant, same tests); untreated controls showed no change (n = 6). The results suggest that reabsorptions seen after inhibition of oxidative processes depend on amiloride-sensitive Na+ channels and glycolytic metabolism.Key words: fetus, lung liquid, 2,4-dinitrophenol, amiloride, iodoacetate.

Effects of lung expansion on lung liquid production in vitro by lungs from fetal guinea-pigs. I. Basic studies and the effects of amiloride and propranolol

1996 ◽  
Vol 8 (3) ◽  
pp. 335 ◽  
Author(s):  
PG Nelson ◽  
AM Perks
Keyword(s):  
Body Weight ◽  
Guinea Pigs ◽  
Receptor Activation ◽  
Lung Damage ◽  
Dilution Method ◽  
Exponential Relationship ◽  
Excessive Pressure ◽  
Lung Expansion ◽  
Lung Liquid

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 62 +/- 2 days of gestation, 97.6 +/- 19.0 (SD) g body weight; n = 134). Untreated control preparations produced fluid at 1.30 +/- 0.22 ml/kg body weight per h, and showed no significant changes during incubation (n = 30). After 1 h of incubation, experimental lungs were expanded with Krebs-Henseleit saline in volumes estimated to be below or approximating those of the first breath (n = 30; first breath, 0.6-1.2 ml). Expansions were graded at 18 +/- 4%, 31 +/- 4%, 43 +/- 3%, 50 +/- 3% and 72 +/- 2% of lung volume (volumes used for expansion at the maximal level, 0.64 +/- 0.25 ml). All expansions of 31% or above produced reductions in fluid production significant by analysis of variance (P < 0.01-0.001); production halted at 50% expansion, and there was strong reabsorption at 72% expansion (-0.87 +/- 0.45 ml/kg body weight per h by the final hour). There was an exponential relationship between percentage expansion and percentage fall in production (r = 1.00). There was no evidence for excessive pressure, and no evidence for lung damage as judged by electron microscopy or entry of intracellular materials into the fluid (lactic dehydrogenase, protein, K+). In studies based on 36 preparations, 10(-6) M amiloride present in the lung lumen (apically) abolished the reabsorptions seen at 70 +/- 3% expansion, but not the arrest of production; it had no effect on control preparations. Studies based on 24 preparations showed that responses to 72 +/- 2% expansion were not affected by 10(-7) M propranolol placed in the outer saline. In studies of 14 fetuses of widely different body weights (68.3-124.9 g), responses to 74 +/- 2% expansion showed an exponential increase with increasing body weight (r = 0.96). Although caution is needed, the results suggest that expansion of the lungs at birth may induce fluid reabsorption by an action independent of tissues outside the lungs, probably involving both activation of a Na(+)-based reabsorptive system and arrest of production, but not requiring beta-receptor activation. The probability that the responses are maximal at birth is discussed, and it is suggested that the effect of expansion may be a specialization of the perinatal lung.

Effects of norepinephrine on lung liquid production by in vitro lungs from fetal guinea pigs

1998 ◽  
Vol 76 (10-11) ◽  
pp. 967-974 ◽  
Author(s):  
S Doe ◽  
B Woods ◽  
A M Perks
Keyword(s):  
Regression Analysis ◽  
Guinea Pigs ◽  
No Reduction ◽  
Dilution Method ◽  
Fluid Reabsorption ◽  
Significant Change ◽  
Near Term ◽  
High Concentrations ◽  
Lung Liquid

Lungs from near-term fetal guinea pigs (61 ± 2 days of gestation) were supported in vitro for 3 h; lung liquid production was monitored by a dye dilution method. Untreated control preparations produced fluid at 1.38 ± 0.30 mL·kg-1 body weight·h-1, with no significant change (ANOVA; regression analysis); those given 1.24 × 10-9 or 1.24 × 10-8 M norepinephrine during the middle hour showed no significant change, but those given concentrations between 5.24 × 10-8 and 1.24 × 10-5 M all showed significant reductions or fluid reabsorption (based on 42 fetuses). The responses showed a linear relationship with the log concentration (r = 0.97). They appeared to involve alpha-adrenoreceptors, since responses to 10-7 M norepinephrine were unaffected by 10-6 M propranolol, but those to 10-7 and 1.24 × 10-6 M norepinephrine were abolished by 10-6 and 1.78 × 10-5 M phentolamine, respectively (based on 48 fetuses). Activation was through alpha2-adrenoreceptors, since responses to 10-7 and 10-5 M norepinephrine were abolished by 10-4 M yohimbine, but not by 10-5 M prazosin (based on 60 fetuses). The results show that norepinephrine is able to reduce lung liquid production when at plasma levels present at birth, and that it can produce reabsorption; unlike epinephrine, there was no reduction in responses at high concentrations. This work reintroduces a neglected factor, norepinephrine, into possible controls of lung liquid reabsorption, and opens up the potential for neural controls.Key words: fetus, norepinephrine, adrenoreceptors, lung liquid.

Pituitary adenylate cyclase-activating peptide and lung-liquid reabsorption in vitro by lungs from fetal guinea-pigs

2002 ◽  
Vol 80 (11) ◽  
pp. 2000-2005 ◽  
Author(s):  
B Li-Pak-Tong ◽  
S Ram ◽  
A M Perks
Keyword(s):  
Adenylate Cyclase ◽  
Guinea Pigs ◽  
Response Curve ◽  
Neuroendocrine System ◽  
Dilution Method ◽  
Partial Recovery ◽  
Pituitary Adenylate Cyclase ◽  
Lung Liquid ◽  
Liquid Removal

Pituitary adenylate cyclase-activating peptide (PACAP) is present in the lungs, notably in their internal neuroendocrine system; however, its use is not clear. It was investigated for its possible ability to cause lung-liquid reabsorption around birth. Lungs from 31 late-term fetal guinea-pigs (at 60 ± 2 days of gestation) were supported in vitro for 3 h; lung-liquid movements were monitored by a dye-dilution method. Untreated control preparations (n = 9) produced fluid at 1.85 ± 0.40 mL·kg–1 body mass·h–1 (mean ± SD), with no significant change (ANOVA, regression analysis). Those given 10–8 M PACAP in the middle hour turned to reabsorption (n = 3) or reduced production markedly (n = 3) (average fall 84.4 ± 5.4%; significant at P < 0.001–0.0005); effects continued and increased after the PACAP was removed. Preparations given 10–9 M PACAP reacted similarly, but there was partial recovery after treatment (five reabsorbed, four reduced production; average fall 91.4 ± 14.3%; significant at P < 0.01–0.0005). Preparations given 10–10 M PACAP all reduced production, with partial recovery (average fall 43.5 ± 8.2%; significant at P < 0.005–0.0005). Preparations given 10–11 M PACAP showed little or no effect. The linear log dose–response curve became maximal at 10–9 M (r2 = 0.98; theoretical threshold 10–13 M). The results increase the likelihood that the neuroendocrine system is important in lung-liquid reabsorption, and suggest that PACAP could combine its relaxation of airways with lung-liquid removal, and therefore aid the first attempts of the newborn to breathe.

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