Possible role during exocytosis of a Ca(2+)-activated channel in neurohypophysial granules.
Ion channels from bovine neurohypophysial granules were incorporated into artificial lipid bilayers. The larger amplitude channel is permeable to cations and exhibits multiple conductances. The channel opens only in the presence of free Ca2+, but is inhibited by relatively high Ca2+ concentrations. Release of vasopressin from permeabilized neurohypophysial terminals also shows a similar biphasic dependence on Ca2+. Release is selectively inhibited by low concentrations of the long-chain alcohol octanol, but not by high concentrations of ethanol, as is the neurosecretory granule Ca(2+)-activated cation channel. Furthermore, Ca(2+)-evoked release and channel activity are both inhibited by the long-chain tetraethylammonium analogs decamethonium and decyl-triethyl ammonium bromide. The close correlation between channel and release properties lead us to conclude that the Ca(2+)-activated channel is involved in peptide secretion.
Lee
C J
CJ
Worcester Foundation for Experimental Biology, Shrewsbury, Massachusetts 01545.
Dayanithi
G
G
Nordmann
J J
JJ
Lemos
J R
JR
D000438:Alcohols / Q000494:pharmacology; D000818:Animals; D001127:Arginine Vasopressin / Q000378:metabolism; D001965:Bromides / Q000494:pharmacology; D002118:Calcium / Q000494:pharmacology*; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology* / Q000648:ultrastructure; D002417:Cattle; D003594:Cytoplasmic Granules / Q000502:physiology* / Q000648:ultrastructure; D003650:Decamethonium Compounds / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity / Q000502:physiology; D005089:Exocytosis / Q000502:physiology*; D015640:Ion Channel Gating / Q000502:physiology; D008051:Lipid Bilayers; D008564:Membrane Potentials / Q000502:physiology; D009411:Nerve Endings / Q000378:metabolism; D010904:Pituitary Gland, Posterior / Q000502:physiology / Q000648:ultrastructure*; D000644:Quaternary Ammonium Compounds
D000438:Alcohols; D001965:Bromides; D015220:Calcium Channels; D003650:Decamethonium Compounds; D008051:Lipid Bilayers; D000644:Quaternary Ammonium Compounds; D001127:Arginine Vasopressin; C051470:ammonium bromide; D002118:Calcium