Summary
The effect of monensin on the secretion of thyroglobulin was studied in open follicles isolated from pig thyroid tissue; in this system, thyroglobulin is secreted into the incubation medium.
When monensin was present during a 4-h chase incubation after pulse-labelling with3H-leucine, the secretion of labelled thyroglobulin was reduced by about 85%; in electron-microscopic autoradiographs of rat thyroid lobes labelled and chase-incubated under similar conditions the relative number of grains over follicle lumina was strongly reduced when monensin was present during the chase. These observations are in agreement with the consensus that monensin arrests transport of secretory proteins in the Golgi complex. In other experiments, pulse-labelled follicles were chase-incubated for 1.5 h whereby labelled thyroglobulin was transported from the RER to exocytic vesicles. Monensin present during a subsequent chase of 0.5 h caused only a moderate decrease of labelled thyroglobulin secretion. TSH present during the second chase-stimulated secretion in both control and monensin-exposed follicles. TSH also caused a drastic reduction of exocytic vesicles in rat thyroid lobes, and the number of vesicles remaining in the cells was the same in controls and lobes exposed to the ionophore.
The observations are interpreted to show that monensin does not inhibit the basal or TSH-stimulated transport of thyroglobulin from the site of monensin-induced arrest in the Golgi complex to the apical cell surface or the exocytosis of thyroglobulin.
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References
Axelsen NH, Bock E (1983) Handbook of Immunoprecipitation in Gel Techniques. Axelsen NH (ed) Scand J Immunol Vol 17, Suppl 10, pp 103–106
Björkman U, Ekholm R (1982) Effect of tunicamycin on thyroglobulin secretion. Eur J Biochem 125:585–591
Björkman U, Ekholm R (1984) Generation of H2O2 in isolated porcine thyroid follicles. Endocrinology 115:392–398
Björkman U, Ekholm R, Elmqvist L-G, Ericson LE, Melander A, Smeds S (1974) Induced unidirectional transport of protein into the thyroid follicular lumen. Endocrinology 95:1506–1517
Björkman U, Ekholm R, Ericson LE, Öfverholm T (1976) Transport of thyroglobulin and peroxidase in the thyroid follicle cell. Mol Cell Endocrinol 5:3–17
Denef J-F, Björkman U, Ekholm R (1980) Structural and functional characteristics of isolated thyroid follicles. J Ultrastruct Res 71:185–202
Ekholm R, Engström G, Ericson LE, Melander A (1975) Exocytosis of protein into the thyroid follicle lumen: An early effect of TSH. Endocrinology 97:337–346
Ericson LE, Engström G (1978) Quantitative electron microscopic studies on exocytosis and endocytosis in the thyroid follicle cell. Endocrinology 103:883–892
Ericson LE, Engström G, Ekholm R (1979) Effects of long term thyroxine treatment in thyrotropin-induced exocytosis and endocytosis in the rat thyroid. Endocrinology 104:704–710
Johanson V, Öfverholm T, Ericson LE (1986) Selective infusion in rat thyroid lobes in vivo. Annales d'endocrinologie, 15th Annual Meeting of the European Thyroid Association, Stockholm 1986. Abstract
Kelly RB (1984) Pathways of protein secretion in eukaryotes. Science 230:25–32
Lowry OH, Rosebrough NJ, Farr AL, Randall RJ (1951) Protein measurement with Folin reagent. J Biol Chem 193:265–275
McIntire FC, Sproull MF (1957) A simple method for determination of desoxypentosenuleic acid in tissue cultures. Proc Soc Exp Biol Med 95:458–461
Öfverholm T, Ericson LE (1984) Rate of protein transport in thyroid follicle cells in normal, thyroxine-treated and TSH-injected rats. Eur J Cell Biol 35:171–179
Tartakoff AM (1983) Perturbation of the structure and function of the Golgi complex by monovalent carboxylic ionophores. Methods Enzymol 98:47–59
Tartakoff AM, Vassalli P (1978) Comparative studies of intracellular transport of secretory proteins. J Cell Biol 79:694–707
Yanagishita M, Hascall VC (1985) Effects of monensin on the synthesis, transport, and intracellular degradation of proteoglycans in rat ovarian granulosa cells in culture. J Biol Chem 260:5445–5455
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Ring, P., Björkman, U., Johanson, V. et al. The effect of monensin on thyroglobulin secretion. Cell Tissue Res. 248, 153–160 (1987). https://doi.org/10.1007/BF01239976
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DOI: https://doi.org/10.1007/BF01239976