Neutral amino acid transport and in vitro aging

Area of Science:

• Cell Biology
• Aging Research
• Biochemistry

Background:

• Human fibroblasts exhibit complex amino acid transport systems.
• Cellular aging is associated with functional changes in various biological processes.
• Amino acid transport is vital for cell metabolism and proliferation.

Purpose of the Study:

• To investigate the impact of in vitro aging on amino acid transport systems in human fibroblasts.
• To quantify the decline in transport rates for specific amino acids with increasing cell population doublings.
• To evaluate the relationship between amino acid transport decline and cellular growth limitations.

Main Methods:

• Culturing human fibroblasts through multiple population doublings.
• Measuring initial transport rates of various amino acids using radiolabeled substrates.
• Assessing the accumulation of specific amino acids within cells.
• Analyzing the effect of substrate concentration on transport rates in young versus aged cells.

Main Results:

• Three out of five distinguishable amino acid transport systems showed decreased initial rates with in vitro aging.
• The L system exhibited a notable decline of 44% in L-phenylalanine transport rate at 10 microM between population doublings 27 and 39.
• L-phenylalanine accumulation within cells was similarly reduced in older fibroblasts.
• Older cells demonstrated reduced sensitivity to lower amino acid concentrations in the culture medium.

Conclusions:

• In vitro aging significantly impairs amino acid transport systems in human fibroblasts, particularly the L system.
• The observed decline in transport capacity may not be the sole or primary factor limiting cellular growth in aged fibroblasts.
• These findings contribute to understanding age-related cellular dysfunction and nutrient uptake mechanisms.