Plasma and urinary metanephrine and normetanephrine concentrations in cats
Pheochromocytoma (PCC) is rare in cats and plasma (PL) and urinary (U) metanephrines (metanephrine [MN]; normetanephrine [NMN]) measurement is rarely described in cats.
In this study, the authors evaluated the utility of PL and U MNs measurement in 10 healthy cats and a cat with a confirmed diagnosis of pheochromocytoma (PheoCat), using liquid chromatography with tandem mass spectrometry (LC-MS-MS).
The research team collected urine and EDTA PL samples from each of the 10 cats and the PheoCat. These samples were promptly stored at -80°C and remained frozen until analysis.
To evaluate U MNs stability, an additional urine sample collected from the healthy cats was refrigerated for 24 hours before freezing. Urinary creatinine concentration (Creat) was assessed using the same spot urine samples to calculate U MNs-to-creatinine ratios.
The PL-MN and PL-NMN median concentrations of the healthy cats were 2.73 and 7.02 nmol/L, respectively. The median U-MN/Creat and U-NMN/Creat ratios were 70 and 139 μg/g, respectively.
The PheoCat had a PL-MN of 3.68 nmol/L, PL-NMN of 66.27 nmol/L, U-MN/Creat of 179 μg/g, and U-NMN/Creat of 1262 μg/g. The PheoCat had markedly increased concentrations of both PL and U MNs when compared to the healthy cats.
Researchers found no significant difference between U MNs measured in urine samples that underwent 24 hours of refrigeration in comparison to those that were frozen immediately.
In conclusion, in this study the authors reported preliminary reference intervals for PL and U MNs in cats using LC-MS-MS and the potential clinical applicability of these biomarkers for the diagnosis of PCC in cats.
Maria Teresa Prego, et al. “Plasma and urinary metanephrine and normetanephrine concentrations using liquid chromatography with tandem mass spectrometry in healthy cats and in a cat with pheochromocytoma.” J Vet Intern Med. 2023 Apr 13. doi: 10.1111/jvim.16648.
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