AJP - Endocrinology and Metabolism, Vol 254, Issue 3 E301-E309, Copyright © 1988 by American Physiological Society
ANF and exocrine pancreas: ultrastructural autoradiographic localization in acinar cells
J. G. Chabot, G. Morel, M. Belles-Isles, L. Jeandel and S. Heisler
Universite Claude Bernard, Faculte de Medecine Lyon-Sud, Oullins, France.
Atrial natriuretic factor (ANF) binding sites have been recently
demonstrated to be present in exocrine pancreas by an in vitro
autoradiographic approach. An autoradiographic study was carried out to
identify the exocrine cells containing ANF binding sites and to monitor the
fate of 125I-labeled ANF in acinar cells after removal of pancreas at
specific time intervals (1-30 min) after intravenous administration. At the
light microscopic level, silver grains were found over acinar and
centroacinar cells. Concomitant injection of an excess of unlabeled ANF
inhibited the binding of labeled peptide by approximately 60%. At the
electron microscopic level, the time-course study in acinar cells has
revealed that of the cell compartments examined, plasma membrane, Golgi
apparatus, mitochondria, and zymogen granules, the nucleus had distinct
labeling patterns. Plasma membrane was maximally labeled 1 and 2 min after
injection with 125I-ANF. Golgi apparatus was significantly labeled from 2
to 30 min after injection, mitochondria from 1 to 30 min after injection,
zymogen granules at 1 and 15 min, and the nucleus only at 30 min. The
lysosomal compartment was not labeled during the 30-min observation period.
These results suggest that after binding to the plasma membrane, ANF is
rapidly internalized and distributed to the intracellular organelles as a
function of time. Labeling of the zymogen granules suggests that they may
bind ANF and that the atrial peptide may be secreted by acinar cells. The
significance of association of radioactivity with mitochondria and nuclei
remains to be elucidated but may represent intracellular sites of action of
ANF complementary to those on plasma membranes.
