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Quantitation of pinocytosis in human monocytes during in vitro maturation into macrophages
1Department of Biological Sciences, University of Keele, Staffordshire, U.K.
Abstract:
Methods are reported for the quantitative measurement of pinocytosis in human monocytes isolated from peripheral blood. The cells, in adherent culture in plastic wells, were exposed for periods of up to 48 h to culture medium containing 125I-labelled polyvinylpyrrolidone (50 micrograms/ml) and the pinocytosis enhancer suramin (500 micrograms/ml). Uptake of radiolabel was linear with time and was inhibited by colchicine (100 micrograms/ml), results that are consistent with uptake of radiolabelled substrate by pinocytosis but not with superficial adsorption of radiolabel. Similar results were obtained using a 125I-labelled vinylamine-vinyl-pyrrolidone copolymer as radiolabelled substrate. The rates of pinocytotic uptake of 125I-labelled polyvinylpyrrolidone (in the presence of suramin) and of 125I-labelled copolymer were measured at various stages of in vitro monocyte-to-macrophage maturation. In contrast to an earlier report, we found no consistent differences in pinocytotic activity between cells at different stages of differentiation.
Insights
This study quantifies pinocytosis in human monocytes using radiolabeled substrates and suramin. Pinocytotic activity did not significantly change during monocyte-to-macrophage differentiation.
Area of Science:
- Cell Biology
- Immunology
- Biochemistry
Background:
- Pinocytosis is a key cellular process for nutrient uptake and immune surveillance.
- Understanding pinocytosis in human monocytes is crucial for immune response research.
- Previous studies suggested varying pinocytotic activity during monocyte differentiation.
Purpose of the Study:
- To develop and validate a method for quantitatively measuring pinocytosis in human monocytes.
- To investigate the effect of suramin as a pinocytosis enhancer.
- To assess pinocytotic activity across different stages of in vitro monocyte-to-macrophage maturation.
Main Methods:
- Human peripheral blood monocytes were cultured and exposed to 125I-labelled polyvinylpyrrolidone or a copolymer.
- Suramin was used as a pinocytosis enhancer, and colchicine as an inhibitor.
- Radiolabel uptake was measured over time and correlated with cellular differentiation.
Main Results:
- Radiolabel uptake was linear with time and confirmed to be pinocytosis, not adsorption.
- Suramin significantly enhanced pinocytotic uptake of the substrates.
- No consistent differences in pinocytotic activity were observed between monocytes and macrophages.
Conclusions:
- A reliable method for quantifying monocyte pinocytosis was established.
- Suramin is an effective enhancer of pinocytosis in human monocytes.
- Monocyte differentiation into macrophages in vitro does not alter basal pinocytotic activity.