Nonselective cation channel as a Ca(2+) influx pathway in pepsinogen-secreting cells of bullfrog esophagus.
In pepsinogen-secreting cells of bullfrog (Rana catesbeiana), recent evidence suggests that Ca(2+) release from internal stores followed by Ca(2+) influx across the plasma membrane elicits pepsinogen secretion. Such a Ca(2+) influx could be carried by a background current, potentiated by bombesin, that was found in these cells using the whole cell patch-clamp technique. The permeability ratio of Cs(+)-Rb(+)-K(+)-Na(+)-Li(+)-N-methyl-D-glucamine(+)-Ca(2+) was 1.01:1:1:0.86:0.72:0.54:0.34. The current was almost totally blocked by the nonselective cation channel blockers La(3+) (0.1 mM) and Gd(3+) (0.1 mM) and was activated by intracellular Ca(2+). These properties demonstrated that the current, which was activated by bombesin, was a nonselective cation current. At the same time, Gd(3+) suppressed pepsinogen secretion by 29 +/- 5.6% in isolated pepsinogen-secreting glands. These results are in accord with the idea that a nonselective cation channel in pepsinogen-secreting cells plays a role as a Ca(2+) influx pathway leading to secretion of pepsinogen in bullfrog esophageal mucosa.
Kimura
S
S
Saiseikai Kure Hospital, Kure City, Hiroshima 737-0821, Japan.
Mieno
H
H
Tamaki
K
K
Inoue
M
M
Chayama
K
K
D000818:Animals; D001839:Bombesin / Q000494:pharmacology; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism*; D020746:Calcium Channels, L-Type / Q000502:physiology; D020013:Calcium Signaling; D002412:Cations / Q000378:metabolism; D002478:Cells, Cultured; D002712:Chlorides / Q000378:metabolism; D004553:Electric Conductivity; D004947:Esophagus / Q000378:metabolism*; D005682:Gadolinium / Q000494:pharmacology; D017136:Ion Transport; D007811:Lanthanum / Q000494:pharmacology; D009543:Nifedipine / Q000494:pharmacology; D018408:Patch-Clamp Techniques; D020116:Pepsinogen A / Q000378:metabolism*; D011892:Rana catesbeiana; D013379:Substrate Specificity
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D020746:Calcium Channels, L-Type; D002412:Cations; D002712:Chlorides; D007811:Lanthanum; D020116:Pepsinogen A; D005682:Gadolinium; D009543:Nifedipine; C038958:gadolinium chloride; D001839:Bombesin