In this study we analyzed several aspects of protein secretion by thyroid follicular cells. The study was carried out on intact thyroid lobes obtained from newborn rats and incubated in vitro. The fate of leucine-3H incorporated into protein within follicular cells of untreated and thyrotropic hormone (TSH)-treated lobes was traced by quantitative electron microscope radioautography. Our findings indicate that protein synthesized by the rough-surfaced endoplasmic reticulum during a pulse exposure to leucine-3H is released relatively slowly by this organelle. Approximately 1 hr after onset of the pulse, a peak of radioactive protein appears in the Golgi region. The significance of this peak is not clear. Newly synthesized secretory protein passes through the apex of follicular cells without being concentrated or temporarily stored there in the form of large secretory droplets. Passage probably takes place via small vesicles which are intermingled among diverse small vesicles at the apex of the cells as well as in the Golgi region. Exposure of the lobes to TSH in the incubation medium for 45 or 90 min does not stimulate incorporation of leucine-3H into protein. Acute stimulation with TSH does, however, modify the movement of secretory protein within the exocrine secretory apparatus of the follicular cell. It accelerates the arrival of the protein at the apex of follicular cells, and it accelerates the release of the protein into the follicular lumen.
Article|
May 01 1972
A BIOCHEMICAL AND RADIOAUTOGRAPHIC ANALYSIS OF PROTEIN SECRETION BY THYROID LOBES INCUBATED IN VITRO
Lynette Feeney,
Lynette Feeney
From the Department of Anatomy, School of Medicine, University of California, San Francisco, California 94122.
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Steven L. Wissig
Steven L. Wissig
From the Department of Anatomy, School of Medicine, University of California, San Francisco, California 94122.
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Lynette Feeney
From the Department of Anatomy, School of Medicine, University of California, San Francisco, California 94122.
Steven L. Wissig
From the Department of Anatomy, School of Medicine, University of California, San Francisco, California 94122.
Dr. Feeney's present address is the Department of Ophthalmology, School of Medicine, University of Oregon, Portland, Oregon 97201.
Received:
December 11 1970
Revision Received:
January 24 1972
Online ISSN: 1540-8140
Print ISSN: 0021-9525
Copyright © 1972 by The Rockefeller University Press
1972
J Cell Biol (1972) 53 (2): 510–522.
Article history
Received:
December 11 1970
Revision Received:
January 24 1972
Citation
Lynette Feeney, Steven L. Wissig; A BIOCHEMICAL AND RADIOAUTOGRAPHIC ANALYSIS OF PROTEIN SECRETION BY THYROID LOBES INCUBATED IN VITRO . J Cell Biol 1 May 1972; 53 (2): 510–522. doi: https://doi.org/10.1083/jcb.53.2.510
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