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ZFIN ID: ZDB-PUB-170712-7
Carbonic Anhydrase Inhibitors Induce Developmental Toxicity During Zebrafish Embryogenesis, Especially in the Inner Ear
Matsumoto, H., Fujiwara, S., Miyagi, H., Nakamura, N., Shiga, Y., Ohta, T., Tsuzuki, M.
Date: 2017
Source: Marine biotechnology (New York, N.Y.)   19(5): 430-440 (Journal)
Registered Authors: Miyagi, Hisako, Nakamura, Nubuhiro
Keywords: Carbonic anhydrase, Embryogenesis, Ethoxyzolamide, Inner ear, Otoliths, Zebrafish
MeSH Terms:
  • Acetazolamide/toxicity*
  • Animal Fins/embryology
  • Animals
  • Apoptosis
  • Calcium/metabolism
  • Carbonic Anhydrase Inhibitors/toxicity*
  • Cardiomegaly/embryology
  • Ear, Inner/embryology
  • Embryo, Nonmammalian/drug effects*
  • Embryonic Development/drug effects
  • Ethoxzolamide/toxicity
  • Hair Cells, Auditory/drug effects
  • Otolithic Membrane/embryology
  • Otolithic Membrane/metabolism
  • Sulfonamides/toxicity*
  • Swimming
  • Thiophenes/toxicity*
  • Zebrafish/embryology*
PubMed: 28695384 Full text @ Mar. Biotechnol.
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ABSTRACT
In vertebrates, carbonic anhydrases (CAs) play important roles in ion transport and pH regulation in many organs, including the eyes, kidneys, central nervous system, and inner ear. In aquatic organisms, the enzyme is inhibited by various chemicals present in the environment, such as heavy metals, pesticides, and pharmaceuticals. In this study, the effects of CA inhibitors, i.e., sulfonamides [ethoxyzolamide (EZA), acetazolamide (AZA), and dorzolamide (DZA)], on zebrafish embryogenesis were investigated. In embryos treated with the sulfonamides, abnormal development, such as smaller otoliths, an enlarged heart, an irregular pectoral fin, and aberrant swimming behavior, was observed. Especially, the development of otoliths and locomotor activity was severely affected by all the sulfonamides, and EZA was a consistently stronger inhibitor than AZA or DZA. In the embryos treated with EZA, inner ear hair cells containing several CA isoforms, which provide HCO3- to the endolymph for otolith calcification and maintain an appropriate pH there, were affected. Acridine orange/ethidium bromide staining indicated that the hair cell damage in the inner ear and pectral fin is due to apoptosis. Moreover, RNA measurement demonstrated that altered gene expression of cell cycle arrest- and apoptosis-related proteins p53, p21, p27, and Bcl-2 occurred even at 0.08 ppm with which normal development was observed. This finding suggests that a low concentration of EZA may affect embryogenesis via the apoptosis pathway. Thus, our findings demonstrated the importance of potential risk assessment of CA inhibition, especially regarding the formation of otoliths as a one of the most sensitive organs in embryogenesis.
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