Ketamine, a
phencyclidine derivative, is an antagonist of the Ca2+-permeable
N-methyl-d-aspartate (
NMDA)-type
glutamate receptors. It is a pediatric
anesthetic and has been implicated in developmental neurotoxicity.
Ketamine has also been shown to deplete
ATP in mammalian cells. Our previous studies showed that
acetyl l-carnitine (
ALCAR) prevented
ketamine-induced
cardiotoxicity and neurotoxicity in zebrafish embryos. Based on our finding that
ALCAR's protective effect was blunted by
oligomycin A, an inhibitor of
ATP synthase, we further investigated the effects of
ketamine and
ALCAR on
ATP levels, mitochondria and
ATP synthase in zebrafish embryos. The results demonstrated that
ketamine reduced
ATP levels in the embryos but not in the presence of
ALCAR.
Ketamine reduced total
mitochondrial protein levels and mitochondrial potential, which were prevented with
ALCAR co-treatment. To determine the cause of
ketamine-induced
ATP deficiency, we explored the status of
ATP synthase. The results showed that a subunit of
ATP synthase, atp5α1, was transcriptionally down-regulated by
ketamine, but not in the presence of
ALCAR, although
ketamine caused a significant upregulation in another
ATP synthase subunit, atp5β and total
ATP synthase
protein levels. Most of the
ATP generated by heart mitochondria are utilized for its contraction and relaxation.
Ketamine-treated embryos showed abnormal heart structure, which was abolished with
ALCAR co-treatment. This study offers evidence for a potential mechanism by which
ketamine could cause
ATP deficiency mediated by
mitochondrial dysfunction.