Effects of insulin and tyrosine kinase inhibitor on ion transport in the alveolar cell of the fetal lung.
We studied the effect of insulin and lavendustin-A (a tyrosine kinase inhibitor) on the short-circuit current (ISC) of primary cultures of fetal distal rat lung epithelium (FDLE). Insulin (2 microM) on the basolateral side of the monolayer increased ISC from 5.76 +/- 0.83 microA/cm2 (SEM, n = 7) to 7.23 +/- 1.00 microA/cm2 (p less than 0.01) under control conditions, and from 1.00 +/- 0.31 microA/cm1 to 1.53 +/- 0.34 microA/cm2 (p less than 0.05, n = 4) when amiloride (10 microM) was present on the apical side of the monolayer. Thus insulin increased both the amiloride-sensitive and insensitive ISC with the insulin-induced increase in ISC in the absence of amiloride (1.47 +/- 0.22 microA/cm2, n = 7) being significantly larger than that in the presence of 10 microM amiloride (0.53 +/- 0.14 microA/cm2, n = 4; p less than 0.025). Insulin's effect reached steady state in 1 hr. Lavendustin-A (10 microM), a tyrosine kinase inhibitor, applied to the apical side of the monolayer attenuated but did not completely block insulin's ability to increase in ISC; i.e., insulin increased ISC in lavendustin-A treated monolayers (0.63 +/- 0.09 microA/cm2, n = 5; p less than 0.0025) but the increase was significantly smaller than that without the pretreatment of lavendustin-A (p less than 0.05). In the presence of amiloride (10 microM) and lavendustin-A (10 microM) insulin was no longer able to increase ISC (change in ISC = 0.04 +/- 0.03 microA/cm2, n = 6), suggesting that lavendustin-A had blocked the insulin's effect on the amiloride-insensitive ISC. Lavendustin-A (10 microM) had no significant effect on the basal ISC in control and amiloride treated monolayers. Our studies demonstrate that insulin increases amiloride-insensitive ISC in FDLE via lavendustin-A sensitive tyrosine kinase and that insulin's action on the amiloride-sensitive ISC of FDLE is mediated through a lavendustin-A insensitive (and presumably tyrosine kinase-independent) pathway.
Hagiwara
N
N
Division of Respiratory Research Hospital for Sick Children Research Institute, University of Toronto Faculty of Medicine, Ontario, Canada.
Tohda
H
H
Doi
Y
Y
O'Brodovich
H
H
Marunaka
Y
Y
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D003994:Bucladesine / Q000494:pharmacology; D002478:Cells, Cultured; D004553:Electric Conductivity; D004848:Epithelium / Q000187:drug effects / Q000196:embryology / Q000502:physiology; D007328:Insulin / Q000494:pharmacology*; D007473:Ion Channels / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D010636:Phenols / Q000494:pharmacology; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011650:Pulmonary Alveoli / Q000187:drug effects / Q000196:embryology* / Q000502:physiology; D051381:Rats
D007328:Insulin; D007473:Ion Channels; D010636:Phenols; C062898:lavendustin A; D003994:Bucladesine; D000584:Amiloride; D011505:Protein-Tyrosine Kinases