Distribution of elements in the pancreatic exocrine cells determined by electron probe X-ray microanalysis

Abstract

We measured the intracellular electrolytes of acinar cells by making electron probe X-ray microanalysis of hydrated and dehydrated sections of freshly frozen dog pancreas. The concentrations of electrolytes in the cytoplasm were: Na 4.8 +/- 2.1, K 132 +/- 15, Cl 14 +/- 4.7, P 165 +/- 36, S 19 +/- 2.8 and in zymogen granules: Na 6 +/- 5, K 60 +/- 16, Cl 31 +/- 20, P 36 +/- 8, S 172 +/- 25, Ca 7 +/- 5 (mean +/- S.D. mmol/kg wet weight). The cytoplasm, which is rich in rough endoplasmic reticulum, had low Na and high K concentrations, as compared with levels in the acinar cells of other exocrine glands such as the submandibular gland, the bulk of which is occupied by secretory granules. Though the representative feature of secretory granules was a high S content, occasionally low S peaks of spectra from secretory granules were obtained. These findings may reflect the content of mature zymogen granules and immature condensing vacuoles. Pilocarpine stimulation increased cytoplasmic Na, Cl and Ca and decreased K levels in the pancreatic acinar cells. This indicates that secretory stimulation increases the permeability of the cell membrane to Na, Cl and K ions and that there is a simultaneous Ca release from the intracellular Ca stores such as zymogen granules and endoplasmic reticulum, and/or Ca influx from the extracellular space.

NAADP, cADPR and IP3 all release Ca2+ from the endoplasmic reticulum and an acidic store in the secretory granule area

“…However, in the secretory granule area, the acidic Ca 2+ store is 30% larger than the ER. Whereas lysosomes have not generally been considered as organelles with a high Ca 2+ content, the secretory granules are known for their high Ca 2+ concentration (Clemente and Meldolesi, 1975;Nakagaki et al, 1984;Nicaise et al, 1992;Thirion et al, 1995;Gerasimenko et al, 1996c). Our experiments with brefeldin A would appear to exclude the Golgi, and the results with GPN to exclude the lysosomes as possible candidate organelles for the thapsigargin-insensitive Ca 2+ store.…”

Electron probe X-ray microanalysis of cellular ions in the eccrine secretory coil cells during methacholine stimulation

“…The fact that the change in [Na] and [K] as determined by helium glow spectrophotometry qualitatively agreed with that of X-ray microanalysis further supports the validity of our methodology and the results. The decrease in cytoplasmic [K] and the increase in [Na] during cholinergic stimulation have also been reported in the rat parotid gland (Izutsu & Johnson, 1986), the dog submandibular acini (Sasaki et al, 1983), and the dog pancreatic acini (Nakagaki et al, 1984). However, in contrast to the sweat secretory coils, [C1] was increased by cholinergic stimulation in these exocrine acini.…”

“…It also appears that the nu- However, this may be partially due to the fact that the myoepithelial cells have higher dry mass fractions than in clear and dark cell cytoplasm and thus the true elemental concentrations are somewhat underestimated (Sauberman, 1986;Smith & Cameron, 1987). The possible origins of tissue S, P and Ca have been speculated in previous reports by others (Nakagaki et al, 1984;Izutsu & Johnson, 1986) and will not be repeated here.…”

Ca2+ and electrolyte mobilization following agonist application to the pancreatic β cell line HIT

“…The special utility programs included some statistical analyses. Details of these procedures are reported elsewhere [32,36]. With frozen hydrated and dehydrated sections of the glands, the dry-mass fractions in the cytoplasm were estimated to be: 23% for normal tissue, 23% for GLP-1-stimulated tissue, 22% for glucose-stimulated tissue and 23% for glucose stimulation in the absence of Ca 2+ .…”