Ultrastructural radioautography of synthesis and migration of proteins and catecholamines in the rat adrenal medulla |
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Authors: | Sarita Benchimol Marc Cantin |
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Affiliation: | (1) Laboratoire de Pathobiologie, Institut de Recherches Cliniques de Montréal, and Département de Pathologie, Université de Montréal, Montréal, Québec;(2) Laboratory of Pathobiology, Clinical Research Institute of Montreal, 110 Pine Ave West, H2W 1R7 Montreal, Québec, Canada |
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Abstract: | Summary The synthetic pathways of proteins and catecholamines in the rat adrenal medullary cells were compared systematically at the ultrastructural level, within a 24 h period, with 2 tracers, L-tyrosine 3,5-3H and L-3,4-dihydroxy [ring 2,5,6-3H] phenylalanine (L-dopa3H). Young rats were injected with either of these tracers and sacrificed in pairs at close time intervals. With L-tyrosine 3H, the label was about equal over rough endoplasmic reticulum (RER) and secretory granules at 2 min after injection and remained almost constant in intensity over the secretory granules throughout the period of observation. A peak of radioactivity was also observed in the Golgi complex between 5 and 20 min after injection. This indicates that L-tyrosine 3H participates in the synthesis of both granule proteins and catecholamines as confirmed by the results obtained after injection of L-dopa 3H. With this tracer, radioactivity over RER, Golgi complex, cytosol and cell surface remained very low at all times and was undetectable at several time intervals. In contrast, radioactivity over secretory granules was very high at all time intervals. The present results thus confirm that in both adrenaline- and noradrenaline-storing cells, the protein moiety of chromaffin granules is synthetized in the RER, packaged in the Golgi complex and rapidly found in newly formed secretory granules. Following either L-tyrosine 3H or L-dopa 3H injection, catecholamine synthesis occurs only in or in close vicinity to chromaffin granules in both cell types at all time intervals.Acknowledgements. This work was supported by a grant from the Medical Research Council of Canada to the Multidisciplinary Research Group of Hypertension of the Clinical Research Institute of Montreal and by the Canadian Heart Foundation |
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Keywords: | Ultrastructural radioautography Protein and catecholamine synthesis Adrenal medulla |
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