Intracellular Ca(2+) channel immunoreactivity in neuroendocrine axon terminals.
The concentration of neuroendocrine terminals in the neurohypophysis facilitates the identification and localization of Ca(2+) channel subtypes near neuroendocrine release sites. Immunoblots of rat neurohypophysial tissue identified the alpha(1)1.3, alpha(1)2.1, alpha(1)2.2, and alpha(1)2.3 Ca(2+) channel subunits. Immunofluorescence staining of axon terminal plasma membranes was weak, suggesting that Ca(2+) channels are dispersed. This contrasts with the highly punctate alpha(1)2.2 immunoreactivity in bovine chromaffin cells; the neurohypophysial terminals may therefore lack the specialized release zones found in those cells. Immunofluorescence and immunogold labeling identify dense core granule-like structures in the terminal cytoplasm containing multiple Ca(2+) channel types. Ca(2+) channels in internal membranes may play an important role in channel targeting and distribution in neuroendocrine cells.
Fisher
T E
TE
Department of Physiology and Biophysics, Mayo Foundation, 1-117 Medical Sciences Building, Rochester, MN 55905, USA. fisher.thomas@mayo.edu
Carrion-Vazquez
M
M
Fernandez
J M
JM
D000818:Animals; D001369:Axons / Q000737:chemistry / Q000648:ultrastructure*; D015220:Calcium Channels / Q000032:analysis*; D002417:Cattle; D002462:Cell Membrane / Q000648:ultrastructure; D019439:Chromaffin Cells / Q000648:ultrastructure; D003594:Cytoplasmic Granules / Q000648:ultrastructure; D015151:Immunoblotting; D008297:Male; D016253:Microscopy, Immunoelectron; D010904:Pituitary Gland, Posterior / Q000737:chemistry* / Q000648:ultrastructure*; D017729:Presynaptic Terminals / Q000737:chemistry / Q000648:ultrastructure*; D051381:Rats; D020318:Rats, Long-Evans
D015220:Calcium Channels