Kinetics of iron import into developing mouse organs determined by a pup-swapping method

Area of Science:

• Biochemistry
• Developmental Biology
• Physiology

Background:

• Dietary iron is essential for early development and organ function.
• Iron transport mechanisms in neonatal mammals are not fully understood.
• Transferrin is traditionally considered the primary iron carrier in plasma.

Purpose of the Study:

• To investigate the kinetics of dietary iron import into various organs of neonatal mice.
• To identify the predominant iron-binding species responsible for organ iron uptake during early development.
• To develop and validate mathematical models for iron import kinetics.

Main Methods:

• Utilized a novel isotopic pup-swapping technique using (56)Fe and (57)Fe.
• Quantified iron concentrations in plasma and organs weekly over 7 weeks.
• Employed Mössbauer spectroscopy to correct for residual blood content and ICP-MS for iron speciation analysis.

Main Results:

• Iron import rates into brain, spleen, heart, and kidneys were highest in the first two weeks of life.
• Liver iron showed net export during the first two weeks, with later peak influx.
• A two-compartment model indicated non-transferrin-bound iron (NTBI) is imported faster into organs than transferrin-bound iron (TBI).

Conclusions:

• NTBI plays a more dominant role than TBI in iron import into organs during early development in healthy mice.
• The findings challenge the traditional view of transferrin as the sole major iron transporter in neonatal circulation.
• This study provides critical insights into neonatal iron metabolism and transport dynamics.