Intracellular electrolyte levels and transport of secretory granules in exocrine gland cells

Sadao Sasaki, Ikuko Nakagaki, Seiki Hori, Hisao Kondo, Bungo Sakaguchi

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

We demonstrate the intracellular transport of secretory granules of a silk protein, fibroin, from the Golgi region to the apical cytoplasm with special reference to microtubule organization, electrolyte concentrations and the acidic intragranular pH of normal and mutant posterior silk gland cells, using the techniques of electrophysiological microelectrode and microprobe analysis and of light and electron microscopic autoradiography. The silk gland cells of a recessive mutant making only flimsy cocoons were defective in the microtubule systems, did not stain with an anti-tubulin antibody in immunofluorescent microscopy, and accumulated intracellular granules in the apical and basal cytoplasm. The increase in intracellular calcium concentration and levels of chloride secretion were also reduced in the mutant cells. A carboxylic ionophore, monensin, which collapsed the granular H+ gradient, induced the transport of chloride and an increase in the intracellular calcium concentration, while it blocked the intracellular transport of granules from the Golgi region to the apical cytoplasm in normal cells. Thus, we conclude that the H+ gradient across the membrane of secretory granules is responsible for the intracellular transport of the secretory granules along the microtubule systems in silk gland cells, while Ca2+ is thought to be required for the exocytosis of the granules.

Original languageEnglish
Pages (from-to)1273-1281
Number of pages9
JournalJournal of Experimental Biology
Volume201
Issue number9
Publication statusPublished - May 1998
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Agricultural and Biological Sciences(all)
  • Agricultural and Biological Sciences (miscellaneous)

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