Summary
The internalization of the extracellular markers horseradish peroxidase (HRP) and cationized ferritin (CF) by the melanotrophs of the intermediate lobe of the rat pituitary was studied during short-time incubation of mechanically dissociated cells or in cell culture after 5 days. After a 30 min exposure, the tracers were found in electron-lucent granules or vacuoles of approximately the same size as the secretory granules, situated 200–500 nm from the cell membrane. In the cultured cells, which showed a higher rate of tracer uptake, internalization was followed for 1, 2 and 5 min after labelling and during 2 h of exposure. Initially, the label was seen only in coated pits and coated vesicles at the cell membrane. Larger vacuoles were first seen after 2–5 min of incubation. After 2 h of exposure the labelling pattern was distinctly different for the two tracers. CF was found in larger vacuoles of varying morphology, in dilatations at the base of cilia, within Golgi saccules and at the edge of the electron-dense core of forming secretory granules. HRP was found in an extensive array of tubulovesicular structures extending throughout the cytoplasm. The Golgi complex and forming granules were, however, not labelled with HRP. The study identifies part of the electron-lucent granules or vacuoles in the melanotroph as endosomes, and shows that the melanotrophs sort CF and HRP via diverting pathways after internalization, suggesting that granule membrane, and possibly its functional components, can be recycled in these cells.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Bäck, N. (1989) The effect of bromocriptine on the intermediate lobe of the rat pituitary: an electron-microscopic, morphometric study. Cell Tissue Res. 255, 405–10.
Bäck, N. (1990) The effect of isoproterenol stimulation on the peripheral zone of the intermediate lobe cells of the rat pituitary - preferential release of electron-lucent granules. Neuroendocrinology 52, 328–31.
Bäck, N., Salminen, K. & Laatikainen, T. (1988) Secretory morphology of the intermediate lobe of the rat pituitary incubated in vitro. Cell Tissue Res. 251, 503–9.
Bácsy, E., Gaal, Gy. & Rappay, Gy. (1985) Lysosomes of the rat pituitary intermediate lobe. Histochem. J. 17, 548–51.
Broadwell, R. D. & Oliver, C. (1983) An enzyme cytochemical study of the endocytotic pathways in anterior pituitary cells of the mouse in vivo. J. Histochem. Cytochem. 31, 325–35.
Carr, J. A., Saland, L. C., Samora, A., Benavidez, S. & Krobert, K. (1991) In vivo effects of serotonergic agents on alpha-melanocyte-stimulating hormone secretion. Neuroendocrinology 54, 616–22.
Darby, N. J. & Smyth, D. G. (1990) Endopeptidases and prohormone processing. Biosci. Rep. 10, 1–13.
DeCamilli, P., Peluchetti, D. & Meldolesi, J. (1976) Dynamic changes of the luminal plasmalemma in stimulated parotid acinar cells. A freeze-fracture study. J. Cell Biol. 70, 59–74.
Douglas, W. W. (1974) Mechanism of release of neurohypophysial hormones: stimulus-secretion coupling. In Handbook of Physiology, Sect 7, Vol IV: The Pituitary Gland and its Neuroendocrine Control, Pt I edited by Greep, R. O. & Astwood, E. B. pp. 191–224. Baltimore: Williams & Wilkins.
Farquhar, M. G. (1978) Recovery of surface membrane in anterior pituitary cells. Variations in traffic detected with anionic and cationic ferritin. J. Cell Biol. 77, R35–42.
Farquhar, M. G. (1982) Membrane recycling in secretory cells: pathway to the Golgi complex. In Membrane Recycling, Ciba Foundation Symposium 92 (edited by Evered, D. & Collins, G. M.) pp. 157–174. London: Pitman Books.
Farquhar, M. G. (1985) Progress in unraveling pathways of Golgi traffic. Ann. Rev. Cell Biol. 1, 447–88.
Gainer, H., Russell, J. T. & Loh, Y. P. (1985) The enzymology and intracellular organization of peptide precursor processing: the secretory vesicle hypothesis. Neuroendocrinology 40, 171–84.
Griffiths, G., Back, R. & Marsh, M. (1989) A quantitative analysis of the endocytotic pathway in baby hamster kidney cells. J. Cell Biol. 109, 2703–20.
Gruenberg, J. & Howell, K. E. (1989) Membrane traffic in endocytosis: insights from cell-free assays. Ann. Rev. Cell Biol. 5, 453–81.
H»kanson, R., Alumets, J., Rehfeld, J. F., Ekelund, M. & Sundler, F. (1982) The life cycle of the gastrin granule. Cell Tissue Res. 222, 479–91.
Helenius, A., Mellman, I., Wall, D. & Hubbard, A. (1983) Endosomes. Trends Biochem. Sci. 8, 245–50.
Herzog, V. & Farquhar, M. G. (1977) Luminal membrane retrieved after exocytosis reaches most Golgi cisternae in secretory cells. Proc. Natl Acad. Sci. USA 74, 5073–7.
Herzog, V. & Miller, F. (1979) Membrane retrieval in epithelial cells of isolated thyroid follicles. Eur. J. Cell Biol. 19, 203–15.
Hubbard, A. L. (1989) Endocytosis. Curr. Opin. Cell Biol. 1, 675–83.
Loh, Y. P. (1987) Peptide precursor processing enzymes within secretory vesicles. Ann. N.Y., Acad. Sci. 493, 292–307.
Lotshaw, D. P., Ye, H. Z. & Edwards, C. (1986) Endocytosis of surface bound dopamine β-hydroxylase and plasma membrane following catecholamine secretion by bovine adrenal chromaffin cells. Neurochem. Int. 9, 391–9.
Mains, R. E. & Eipper, B. A. (1979) Synthesis and secretion of corticotropins, melanotropins, and endorphins by rat intermediate pituitary cells. J. Biol. Chem. 254, 7885–94.
Mains, R. E., Cullen, E. I., May, V. & Eipper, B. A. (1987) The role of secretory granules in peptide biosynthesis. Ann. N.Y. Acad. Sci. 493, 278–91.
May, V., Stoffers, D. A. & Eipper, B. A. (1989) Proadrenocorticotropin/endorphin production and messenger ribonucleic acid levels in primary intermediate pituitary cultures: effects of serum, isoproterenol, and dibutyryl adenosine 3′,5′-monophosphate. Endocrinology 124, 157–66.
Morris, J. F. & Nordmann, J. J. (1982) Membrane retrieval by vacuoles after exocytosis in the neural lobe of Brattleboro rats. Neuroscience 7, 1631–9.
Morris, J. F., Nordmann, J. J. & Dyball, R. E. J. (1978) Structurefunction correlation in mammalian neurosecretion. Int. Rev. Exp. Pathol. 18, 1–95.
Mortensen, N. J. M. & Morris, J. F. (1977) The effect of fixation conditions on the ultrastructural appearance of gastrin cell granules in the rat gastric pyloric antrum. Cell Tissue Res. 176, 251–63.
Oliver, C. & Hand, A. H. (1978) Uptake and fate of luminally administered horseradish peroxidase in resting and isoproterenol-stimulated rat parotid acinar cells. J. Cell Biol. 76, 207–20.
Oliver, C., Tolbert, C. L. & Waters, J. F. (1989) Internalization of horseradish peroxidase isozymes by pancreatic acinar cells in vitro. J. Histochem. Cytochem. 37, 49–56.
Patzak, A. & Winkler, H. (1986) Exocytotic exposure and recycling of membrane antigens of chromaffin granules: ultrastructural evaluation after immunolabeling. J. Cell Biol. 102, 510–5.
Pelletier, G. (1973) Secretion and uptake of peroxidase by rat adenohypophyseal cells. J. Ultrast. Res. 43, 445–59.
Randle, J. C. R., Moor, B. C. & Kraicer, J. (1983) Differential control of the release of pro-opiomelanocortin-derived peptides from the pars intermedia of the rat pituitary. Response to serotonin. Neuroendocrinology 37, 131–40.
Rechardt, L., Kanerva, L. & Hervonen, H. (1977) Ultrastructural demonstration of amine granules in the adrenal medullary cells of the rat using acid permanganate fixation. Histochemistry 54, 339–43.
Rodman, J. S., Mercer, R. W. & Stahl, P. D. (1990) Endocytosis and transcytosis. Curr. Opin. Cell Biol. 2, 664–72.
Rosenzweig, L. J. & Kanwar, Y. S. (1984) Quantitative determination of the intracellular fate of internalized plasma membrane in dissociated pituitary prolactin cells utilizing a radioiodinated cationic ferritin probe (CFI*) and electron microscopic autoradiography. Am. J. Anat. 169, 193–206.
Sandvig, K., Olsnes, S., Petersen, O. W. & VanDeurs, B. (1987) Acidification of the cytosol inhibits endocytosis from coated pits. J. Cell Biol. 105, 679–89.
Schnabel, E., Mains, R. E. & Farquhar, M. G. (1989) Proteolytic processing of pro-ACTH/endorphin begins in the Golgi complex of pituitary corticotropes and AtT-20 cells. Mol. Endocrinol. 3, 1223–35.
Schwartz, A. L. (1990) Cell biology of intracellular protein trafficking. Ann. Rev. Immunol. 8, 195–229.
Swann, R. W. & Pickering, B. T. (1976) Incorporation of radioactive precursors into the membrane and contents of the neurosecretory granules of the rat neurohypophysis as a method of studying their fate. J. Endocr. 68, 95–108.
Theodosis, D. T. (1983) Intracellular membrane movements associated with hormone release in magnocellular neurones. Progr. Brain Res. 60, 273–9.
Thyberg, J. (1980) Internalization of cationized ferritin into the Golgi complex of cultured mouse peritoneal macrophages. Effects of colchicine and cytochalasin B. Eur. J. Cell Biol. 23, 95–103.
Tilders, F. J. H., Post, M., Jackson, S., Lowry, P. J. & Smelik, P. G. (1981) Beta-adrenergic stimulation of the release of ACTH and LPH-related peptides from the pars intermedia of the rat pituitary gland. Acta Endocrinol. 97, 343–51.
VanDeurs, B., Petersen, O. W., Olsnes, S. & Sandvig, K. (1989) The ways of endocytosis. Int. Rev. Cytol. 117, 131–77.
VonGrafenstein, H., Roberts, C. S. & Baker, P. F. (1986) Kinetic analysis of the triggered exocytosis/endocytosis secretory cycle in cultured bovine adrenal medullary cells. J. Cell Biol. 103, 2343–52.
Winkler, H. (1988) Occurrence and mechanism of exocytosis in adrenal medulla and sympathetic nerve. In Handbook of Experimental Pharmacology, Vol 90/I (edited by Trendelenburg, U. & Weiner, N.) pp. 43–118. Berlin, Heidelberg: Springer-Verlag.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Bäck, N., Soinila, S. & Virtanen, I. Endocytotic pathways in the melanotroph of the rat pituitary. Histochem J 25, 133–139 (1993). https://doi.org/10.1007/BF00157985
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00157985