Subunit composition and role of Na+,K+-ATPases in adrenal chromaffin cells.
Adrenal medullary (AM) cells are exposed to high concentrations of cortical hormones, one of which is a ouabain-like substance. Thus, the effects of ouabain on catecholamine secretion and distribution of Na+,K+-ATPase alpha and beta subunits in rat and guinea-pig AM cells were examined using amperometry and immunological techniques. While exposure to 1 microm ouabain did not have a marked effect on resting secretion, it induced an increase in secretion due to mobilization of Ca2+ ions that were stored during a 4 min interval between muscarine applications. Immunocytochemistry revealed that Na+,K+-ATPase alpha1 subunit-like and beta3 subunit-like immunoreactive (IR) materials were distributed ubiquitously at the cell periphery, whereas alpha2- and beta2-like IR materials were present in restricted parts of the cell periphery. The alpha1 and alpha2 subunits were mainly immunoprecipitated from AM preparations by anti-beta3 and anti-beta2 antisera, respectively. Peripheral BODIPY-FL-InsP3 binding sites were localized below membrane domains with alpha2- and beta2-like IR materials. The results indicate that in AM cells, alpha1beta3 isozymes of Na+,K+-ATPase were present ubiquitously in the plasma membrane, while alpha2beta2 isozymes were in the membrane domain closely associated with peripheral Ca2+ store sites. This close association of the alpha2beta2 isozyme with peripheral Ca2+ store sites may account for the facilitation of mobilization-dependent secretion in the presence of 1 microm ouabain.
Lin
Hai
H
Department of Physiology, Fukuoka University School of Medicine, Fukuoka, Japan.
Ozaki
Shoichiro
S
Fujishiro
Naoji
N
Takeda
Kazuo
K
Imanaga
Issei
I
Prestwich
Glenn D
GD
Inoue
Masumi
M
D000313:Adrenal Medulla / Q000187:drug effects / Q000201:enzymology*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000201:enzymology; D019439:Chromaffin Cells / Q000187:drug effects / Q000201:enzymology*; D006168:Guinea Pigs; D007527:Isoenzymes / Q000737:chemistry / Q000502:physiology; D010042:Ouabain / Q000494:pharmacology; D021122:Protein Subunits / Q000737:chemistry* / Q000502:physiology*; D051381:Rats; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000502:physiology*
D007527:Isoenzymes; D021122:Protein Subunits; D010042:Ouabain; D000254:Sodium-Potassium-Exchanging ATPase