Element accumulation in the tracheal and bronchial cartilages of monkeys

Compositional changes in the tracheal and bronchial cartilages can affect respiratory ventilation and lung function. We aimed to elucidate element accumulation in the tracheal and bronchial cartilages of monkeys and divided it into four sites: tracheal, tracheal bifurcation, left bronchial, and right bronchial cartilages. The elemental content was analyzed using inductively coupled plasma atomic emission spectrometry. The average calcium content was two to three times higher in the tracheal cartilage than in the other three cartilages. The trends of phosphorus and zinc were similar to those of calcium. The average calcium, phosphorus, and zinc contents were the highest in the tracheal cartilage and decreased in the following order: the left bronchial, right bronchial, and tracheal bifurcation cartilages. These findings revealed that differences existed in element accumulation between different sites within the same airway cartilage and that calcium, phosphorus, and zinc accumulation mainly occurred in the tracheal cartilage. A substantial direct correlation was observed between age and calcium content in the tracheal and bronchial cartilages and all such monkeys with high calcium content were > four years of age. These results suggest that calcium accumulation occurs in the tracheal and bronchial cartilages after reaching a certain age. An extremely substantial direct correlation was observed between calcium and phosphorus contents in the tracheal and bronchial cartilages. This finding is similar to the previously published calcium and phosphorus correlations in several other cartilages, suggesting that the calcium and phosphorus contents of cartilage exist in a certain ratio. ### Competing Interest Statement The authors have declared no competing interest.