Effect of colchicine on internalization of prolactin in female rat liver: an in vivo radioautographic study.

Abstract

Binding and internalization of 12Sl-ovine prolactin into hepatocytes of female rats was visualized by the in vivo radioautographic method (Bergeron, J. J. M., G. Levine, R. Sikstrom, D. O'Shaughnessey, B. Kopriwa, N. J. Nadler, and B. I. Posner, 1977, Prec. NatL Acad. Sci. USA, 745:051-5055). Receptor-mediated internalization of label was observed into lipoprotein-filled vesicles in the Golgi/bile canalicular region of the hepatocyte. Colchicine treatment had no effect on the internalization of label into the lipoprotein-filled vesicles. However, the location of the radio-labeled lipoprotein-filled vesicles was altered from the Golgi/bile canalicular region to subsinusoidal. Radioactive content of hepatocytes decreased as a function of time after injection of 12~l-prolactin; however, colchicine treatment markedly retarded this loss of label. Subcellular fractionation experiments indicated that colchicine treatment led to decreased levels of ~2~l-protactin accumulation in microsomes but augmented the accumulation of label in the L fraction.It is concluded that in normal female rats prolactin is internalized into lipoprotein-filled vesicles in the Golgi region before degradation of the hormone. Colchicine treatment accumulates labeled lipoprotein-containing vesicles in a subsinusoidal region and retards hormone catabolism. The labeled vesicles observed after colchicine treatment may correspond to the unique vesicles previously observed in the L fraction and found to be enriched in prolactin receptors

Specific binding of endocrine transforming growth factor-beta 1 to vascular endothelium.

“…1 c). Non-receptor-mediated clearance of polypeptide hormones by the proximal convoluted tubule has been previously demonstrated ( 17,40). Quantitation of the LM radioautographic observations confirmed that the binding to the glomeruli but not to the proximal convoluted tubules was specific (Table I).…”

“…This technique of in vivo injection and radioautography has been used to visualize insulin (16), prolactin (17), calcitonin (18), parathyroid hormone (19), epidermal growth factor (20,21), atrial natriuretic factor (22), angiotensin II (23), and ACTH (24) binding to receptors on target cells in vivo. These experiments revealed previously unrecognized binding sites relevant to the physiological functions of the cognate ligands.…”

Preparation of microtubules from rat liver and testis: Cytoplasmic dynein is a major microtubule associated protein

“…A similar mechanism seems to be behind the juxtanuclear localization of lysosomes in many cell types [Herman and Albertini, 1984;Matteoni and Kreis, 19871. Evidence has also been obtained for a role of microtubules in the transport of endosomes from the cell margin and subsequent transfer of material to lysosomes [Bergeron et a]., 1983;Oka and Weigel, 1983;Hornick et al, 19841 and finally to Golgi [Posner et al, 19821. Based on the prekent findings, cytoplasmic dynein is a clear candidate for a role in these more general motilc processes in the cells of liver and testis and probably other cell types as well [Schroer et al, 19891.…”

Insulin and α2‐macroglobulin‐methylamine undergo endocytosis by different mechanisms in rat adipocytes: I. Comparison of cell surface events

“…In contrast, the mechanisms by which peptide hormones undergo endocytosis are less thoroughly understood. Coated pits have been observed to mediate the endocytosis of certain peptide hormones but not others (Amsterdam et al, 1981; Barazzone et al, 1980; Bergeron et al, 1983; Carpentier et al, 1985; Draznin et al, 1985; Dunn and Hubbard, 1984; Jennes et al, 1983; Nilsson et al, 1983; Smith and Jarett, 1983).…”