Element distribution in organelles of pancreatic acinar cells of rat, mouse, and pig investigated by energy-dispersive X-ray microanalysis.
The exocrine pancreas was long thought to be composed of identical subunits, the acinar cells that store the inactive forms of the digestive enzymes in zymogen granules (ZGs). These were generally seen as a homogeneous population of vesicles. This homogeneity was recently questioned: Digestive demands are answered by the release of specific enzymes and immunocytochemical labeling showed distinctive nonidentical populations of ZGs. We have aimed at finding concomitant differences in element contents. We analyzed by energy-dispersive x-ray microanalysis (EDX) the subcellular distribution of elements in acinar cells of resting and stimulated rat, resting mouse, and resting pig pancreas and compared the results with values from the literature. We found large variances in the concentrations of Na, Mg, P, S, Cl, K, and Ca in cytoplasm rich in endoplasmic reticulum (C/E), whereas the concentrations of P, Cl, K, and Ca in mitochondria and ZGs had surprisingly small variations. Na and Mg were detected in measurable amounts only in C/E and mitochondria and Ca was detectable only in ZGs. We could not find any other elements. We have not found clearly distinguishable populations of ZGs. We critically discuss our findings in comparison with the literature. Many discrepancies can be explained by the different preparation procedures. We show that it is questionable to present absolute values of concentration in biological specimens on the basis of EDX. The technique should, in our opinion, be used only for the study of relative concentrations.
Tobler
M
M
Departement für Innere Medizin, Universitätsspital Zürich, Switzerland.
Zierold
K
K
Ammann
R W
RW
Freiburghaus
A U
AU
D000818:Animals; D004577:Electron Probe Microanalysis; D004602:Elements; D004721:Endoplasmic Reticulum / Q000737:chemistry; D005260:Female; D051379:Mice; D008813:Mice, Inbred ICR; D008928:Mitochondria / Q000737:chemistry; D015388:Organelles / Q000737:chemistry*; D010179:Pancreas / Q000737:chemistry* / Q000648:ultrastructure; D051381:Rats; D011919:Rats, Inbred Strains; D015203:Reproducibility of Results; D013045:Species Specificity; D013552:Swine
D004602:Elements