Plasma Retention and Systemic Kinetics of 90Sr Intramuscularly Injected in Female Nonhuman Primates

Area of Science:

• Radiological Sciences
• Toxicology
• Comparative Physiology

Background:

• Strontium (Sr) biokinetics are crucial for internal dose assessment in radiological protection.
• Existing biokinetic models for strontium are primarily based on human data.
• Nonhuman primates (NHPs) offer a valuable model for studying human radioelement metabolism.

Purpose of the Study:

• To compare strontium biokinetic data in Rhesus macaques with established human models.
• To investigate the influence of dietary calcium on strontium metabolism in NHPs.
• To assess the applicability of current models for extrapolating animal data to humans.

Main Methods:

• Thirteen female Rhesus macaques were administered strontium nitrate (Sr(NO3)2) intramuscularly.
• Biokinetic data (plasma, urine, feces, skeletal retention) were collected over time.
• Measured activities were compared against predictions from NCRP 156 and ICRP systemic models.

Main Results:

• NHP plasma strontium activities were consistently lower than human model predictions.
• Urinary excretion in NHPs was significantly higher than in humans, especially early post-injection.
• Skeletal retention of strontium in NHPs was lower compared to humans, attributed to higher dietary calcium.

Conclusions:

• Dietary calcium significantly influences strontium metabolism, particularly urinary excretion and skeletal retention.
• NHP strontium biokinetics exhibit notable differences from human models, necessitating careful consideration during interspecies extrapolation.
• Variability in animal and human strontium metabolism underscores the need for refined biokinetic models.