Pinocytosis in fibroblasts. Quantitative studies in vitro

Area of Science:

• Cell Biology
• Biochemistry

Background:

• Pinocytosis is a key cellular process for internalizing extracellular material.
• Understanding pinocytosis rates and metabolic requirements is crucial for cell biology research.

Purpose of the Study:

• To quantify the rate of pinocytosis in fibroblast cell lines using horseradish peroxidase (HRP).
• To investigate the metabolic requirements and characteristics of pinocytosis in L cells.

Main Methods:

• Utilized horseradish peroxidase (HRP) as a fluid-phase marker to measure pinocytosis rates.
• Assessed HRP uptake in various fibroblast cell lines, including L cells.
• Investigated the effects of temperature and metabolic inhibitors on pinocytosis in L cells.
• Measured cellular ATP levels to understand energy pathways supporting pinocytosis.

Main Results:

• HRP was internalized via fluid-phase pinocytosis without cell surface adsorption.
• Pinocytosis rate was proportional to HRP concentration and exposure time.
• L cells exhibited increased pinocytic activity post-confluence and inactivated HRP with a 6-8 hour half-life.
• Pinocytosis increased with temperature (Q(10)=2.7) and required both glycolytic and respiratory ATP production in L cells.

Conclusions:

• Established a quantitative assay for pinocytosis using HRP in fibroblasts.
• Demonstrated that L cells utilize both glycolytic and respiratory pathways for ATP synthesis to support pinocytosis.
• The precise physiological function of pinocytosis in tissue culture cells remains undetermined.