Blood sampling procedures influence serum calcitonin concentrations in rats

The aim of this study was to determine whether serum calcitonin (S-CT) in rats is influenced by the method of taking blood samples. Sampling during halothane anaesthesia, after repeated administration of anaesthesia after a 14-day interval, and sampling without the use of anaesthetics (i.e. after the rats were made unconscious by stunning), resulted in different S-CT values (P < or = 0.001), whereas Ca2+ levels were not affected. In thyroidectomized rats, the S-CT values after stunning were not significantly different whereas those in sham-operated rats were different (P < or = 0.01). The possibility that anaesthesia may suppress stunning-induced changes in S-CT was explored in three other groups of rats subjected to halothane anaesthesia, stunning and stunning under halothane anaesthesia respectively. Although the S-CT level was highest after stunning and lowest in halothane-anaesthetized rats (P < or = 0.001), anaesthesia did not suppress the effect of stunning on S-CT. In conclusion the effect of sampling procedures must be considered in studies on the levels of S-CT in rats.