Stability of plasma intact FGF23 levels as compared to increasing C-terminal FGF23 during short term experimental conditions. Monitoring of iFGF23 resulted in stable levels, while levels of cFGF23 increased significantly already within 1 hour (p < 0.05), and remained elevated for 2 hours (p < 0.01). This increase of cFGF23 was seen both in non-anesthetized, awake rats and anesthetized rats and was similar for the two different anesthetics used. The rats were not subject to further intervention. Mean ± SEM. *p < 0.05 vs 0 min, **p < 0.01 vs 0 min.