Normal Levels of Urinary CC16 Protein. Comments on Beamer et al. Association of Children's Urinary CC16 Levels with Arsenic Concentrations in Multiple Environmental Media. Int. J. Environ. Res. Public Health 2016, 13, 521/Reply

A proximal tubular dysfunction results in the diminished resorption of CC16 and increased levels in the urine. Since the early 1990s, the determination of urinary CC16 has sporadically been used as a marker of tubular renal proximal dysfunction [4]. Later, it was confirmed that chronic arsenic administration in experimental animals originates ultrastructural alterations that consist in swollen mitochondria and increased numbers of dense autophagic lysosome-like bodies in the proximal tubule cells [7]. [...]a subcytotoxic dose of arsenite induces necrotic changes in the cytoplasmic structure and mitochondrial morphology in the human proximal tubular cell line [8]. Under physiological conditions, the quasi-totality of this protein that is filtered is reabsorbed in the proximal tubule in such a way that the detectable levels in urine are very low. [...]in our first paper on the subject, the value of the urinary CC16-to-creatinine ratio was zero in 16 of the 31 control children (51.6%) [12].