Determining biological tissue turnover using stable isotopes: the reaction progress variable.

Area of Science:

• Biogeochemistry
• Ecological Physiology
• Isotope Ecology

Background:

• Stable isotope analysis is crucial for understanding animal ecology and physiology.
• Existing models for isotope turnover often struggle with multiple pools or varying experimental conditions.
• Accurate reconstruction of diet histories and understanding tissue turnover are vital research areas.

Purpose of the Study:

• To develop a novel method using a reaction progress variable for stable isotope turnover analysis in biological tissues.
• To enable the determination of multiple isotope turnover pools within biological systems.
• To create a flexible model applicable to various growth rates and experimental designs.

Main Methods:

• Application of the reaction progress variable to stable isotope turnover data.
• Normalization process allowing integration of experiments with differing initial/final isotope compositions.
• Incorporation of time-series isotope measurements for diet history reconstruction.
• Quantification of delayed release from bone marrow and mass-dependent turnover.

Main Results:

• The reaction progress variable effectively identifies the presence of multiple isotope turnover pools.
• The model successfully integrates data from multiple experiments with varying isotope compositions.
• Accurate animal diet histories can be calculated using sequential isotope measurements.
• Delayed blood cell release and mass-corrected turnover are quantifiable.
• The approach accommodates various growth models beyond exponential growth.

Conclusions:

• The reaction progress variable offers a robust framework for analyzing complex stable isotope dynamics in biological tissues.
• This method enhances the accuracy of diet reconstruction and physiological turnover studies.
• The model's flexibility makes it broadly applicable to diverse ecological and physiological research questions, including those involving animal growth.