Amiloride-blockable Ca2+-activated Na+-permeant channels in the fetal distal lung epithelium |
| |
Authors: | Yoshinori Marunaka |
| |
Affiliation: | (1) MRC Group in Lung Development and Division of Respiratory Research, The Hospital for Sick Children Research Institute, The university of Toronto Faculty of Medicine, M5G 1X8 Toronto, Ontario, Canada |
| |
Abstract: | The Na+ transport function of alveolar epithelium represents an important mechanism for clearance of fluid in air space at birth. I observed the activity of two types of amiloride-blockable Na+-permeant cation channels in the apical membrane of fetal distal lung epithelium cultured on permeable filters for 2 days after harvesting of the cells from Wistar rats of 20 days' gestation (term = 22 days). One type was a nonselective cation (NSC) channel and had a linear current/voltage (I/V) relationship with a single-channel conductance of 26.9 ± 0.8 pS (n = 5). The other type was highly Na+ selective (i.e. Na+ channel) and had an inwardly rectifyingI/V relationship with a single-channel conductance of 11.8 ± 0.2 pS (n = 5) around resting membrane potential. The NSC channel was more frequently observed (1.37 ± 0.15 per patch membrane;n = 73) than the Na+ channel (0.15 ± 0.40 per patch membrane;n = 73). However, the open probability of the NSC channel was smaller than that of the Na+ channel. Both types of the channels were activated by cytosolic Ca2+, however the sensitivity to cytosolic Ca2+ was much higher in the Na+ channel than in the NSC channel. Furthermore, both types of the channels were blocked by amiloride or benzamil. The half-maximal inhibitory concentration (IC50) of amiloride or benzamil of the Na+ channel was 1–2 M, while that of NSC channel was less than 1 M. Both channels were activated by insulin. |
| |
Keywords: | Benzamil Insulin Nonselective cation channel Na+ channel Alveolar cells Type II Single-channel recording |
本文献已被 SpringerLink 等数据库收录! |
|