Ionic factors affecting the association of tyrosine hydroxylase with chromaffin granules in the adrenal medullary cell.
Chromaffin cells were treated with digitonin in medium containing various ions and the efflux of tyrosine hydroxylase from these permeabilized cells was then determined to elucidate a possible influence of cytoplasmic ionic environment on the association of this enzyme with the chromaffin granule. The enzyme efflux was observed with a distinct lag during exposure to low concentrations of digitonin in the medium containing isotonic sucrose. In contrast, a larger extent of the enzyme efflux was observed without any notable delay in the presence of isotonic NaCl. The results were thought to indicate the possibility that the dissociation of soluble enzyme from the granule surface within the permeabilized cells might occur in the presence of NaCl. Furthermore, the interaction between tyrosine hydroxylase and isolated chromaffin granule membranes was directly examined, and this interaction was shown to be inhibited by NaCl. However, the enzyme-granule membrane interaction was also inhibited by KCl and choline chloride. It therefore seems possible to consider that the inhibitory action of NaCl on the association of soluble enzyme with the granule may not be due to the specific action of Na+, but presumably due to the non-specific chaotropic effect of Cl-. On the other hand, the enzyme efflux was markedly reduced by the presence of Ca2+ in the permeabilizing medium, but the enzyme-granule membrane interaction was not affected by Ca2+ at the same concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)
Department of Pharmacology, Tokushima University School of Medicine, Japan.
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K
Morita
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Hamano
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M
Oka
D000313:Adrenal Medulla / Q000378:metabolism*; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D002412:Cations / Q000494:pharmacology*; D002417:Cattle; D002837:Chromaffin Granules / Q000737:chemistry / Q000378:metabolism*; D066298:In Vitro Techniques; D009994:Osmolar Concentration; D011188:Potassium / Q000494:pharmacology; D012964:Sodium / Q000494:pharmacology; D014446:Tyrosine 3-Monooxygenase / Q000378:metabolism*
D002412:Cations; D012964:Sodium; D014446:Tyrosine 3-Monooxygenase; D011188:Potassium; D002118:Calcium