Endocytosis and degradation of ovine prolactin by Nb2 lymphoma cells: characterization and effects of agents known to alter prolactin-induced mitogenesis

Endocrinology
E C Augustine, R S Kensinger

Abstract

Rat Nb2 node lymphoma cells proliferate in response to lactogens, but the signal transduction mechanism involved remains unclear. Specific binding, internalization, and degradation of ovine PRL (oPRL) were examined under a variety of experimental conditions to characterize the metabolism of receptor-bound hormone by these cells. Stationary-phase cells were incubated with [125I]oPRL in Fischer's medium containing horse serum. Cell suspensions were centrifuged, and the cell pellets were assayed to determine specific cell-associated radioactivity. Internalized ligand was measured by exposing the cells to an acidic buffer before centrifugation to dissociate hormone from plasma membrane receptors, and cell-surface ligand was calculated by subtracting internalized hormone from the total [125I]oPRL bound by the cells. Hormone degradation was assessed by measuring the radioactivity in an acid-soluble fraction prepared from the incubation medium. Endocytosis of [125I]oPRL was observed within 30 min at 37 C, and the internalized component accounted for approximately 50% of the bound hormone under steady-state conditions. Hormone degradation was detectable within 1 h at 37 C and continued at a relatively linear rate thereafter; by 4 h, 8%...Continue Reading

Citations

Jul 1, 1992·Immunology Letters·K Skwarło-Sońta
Mar 1, 1996·Domestic Animal Endocrinology·M Khosraviani, S L Davis
May 1, 1996·Baillière's Clinical Rheumatology·I BercziR J Warrington
Jul 1, 1992·Archives of Biochemistry and Biophysics·A R BuckleyC W Putnam

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