Isolated secretion granules from parotid glands of chronically stimulated rats possess an alkaline internal pH and inward-directed H/sup +/ pump activity

Journal Article · Wed Oct 01 04:00:00 EDT 1986 · J. Cell Biol.; (United States)

DOI:https://doi.org/10.1083/jcb.103.4.1257· OSTI ID:6477236

Arvan, P; Castle, J D

Secretion granules have been isolated from the parotid glands of rats that have been chronically stimulated with the ..beta..-adrenergic agonist, isoproterenol. These granules are of interest because they package a quantitatively different set of secretory proteins in comparison with granules from the normal gland. Polypeptides enriched in proline, glycine, and glutamine, which are known to have pI's >10, replace ..cap alpha..-amylase (pI's = 6.8) as the principal content species. The internal pH of granules from the treated rats changes from 7.8 in a potassium sulfate medium to 6.9 in a choline chloride medium. The increased pH over that of normal parotid granules (approx.6.8) appears to protect the change in composition of the secretory contents. Whereas normal mature parotide granules have practically negligible levels of H/sup +/ pumping ATPase activity, the isolated granules from isoproterenol-treated rats undergo a time-dependent internal acidification that requires the presence of ATP and is abolished by an H/sup +/ ionophore. Additionally, an inside-positive granule transmembrane potential develops after ATP addition that depends upon ATP hydrolysis. Two independent methods have been used that exclude the possibility that contaminating organelles are the source of the H/sup +/-ATPase activity. Together these data provide clear evidence for the presence of an H/sup +/ pump in the membranes of parotid granules from chronically stimulated rats. However, despite the presence of H/sup +/-pump activity, fluorescence microscopy with the weak base, acridine orange, reveals that the intragranular pH in live cells is greater than that of the cytoplasm.

• Research Organization: Yale Univ. School of Medicine, New Haven, CT
• OSTI ID: 6477236
• Journal Information: J. Cell Biol.; (United States), Journal Name: J. Cell Biol.; (United States) Vol. 103:4; ISSN JCLBA
• Country of Publication: United States
• Language: English

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