Effect of betaxolol on aspartate aminotransferase activity in hypoxic rat retina in vitro.
We investigated the effect of betaxolol on the decrease of mitochondrial aspartate aminotransferase (mAAT) activity in rat retinas induced by hypoxia in vitro. It is reported that mAAT decreases in ischemic or hypoxic retina and that the decrease is caused by Ca(2+)-dependent proteases such as calpain. Betaxolol is a compound that has beta(1)-adrenergic receptor blocking and voltage-dependent calcium channel blocking properties. The rat eye cups were maintained with Locke's solution saturated with 95% air - 5% CO(2). The eye cups were immersed in glucose-free Locke's solution saturated with 95% N(2) / 5% CO(2) (hypoxic solution). Ninety minutes of hypoxia caused a 20% decrease in mAAT activity. The eye cups incubated with the hypoxic solution containing 1 mM EGTA, 10 micro M MK-801 or 100 micro M betaxolol were protected from the decrease in mAAT activity, so that the residual mAAT activity was 50%, 45% or 40%, respectively, compared to the eye cups incubated in hypoxic solution alone, which had a 100% decrease in mAAT activity. In addition, co-incubation with EGTA and betaxolol had a greater protective effect against the mAAT decrease than a single application. This additive effect of betaxolol was dose-dependent. These results suggested that betaxolol had a protective effect against the decrease of mAAT caused by hypoxia and indicated that betaxolol might inhibit the Ca(2+) release from intracellular Ca(2+) stores.
Endo
Satoko
S
Department of Ophthalmology, Tohoku University School of Medicine, Japan.
Tomita
Hiroshi
H
Ishiguro
Sei-Ichi
S
Tamai
Makoto
M
D000818:Animals; D024442:Aspartate Aminotransferase, Mitochondrial / Q000378:metabolism*; D015784:Betaxolol / Q000008:administration & dosage / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D016291:Dizocilpine Maleate / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D000860:Hypoxia / Q000201:enzymology / Q000378:metabolism*; D066298:In Vitro Techniques; D018696:Neuroprotective Agents / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D012160:Retina / Q000187:drug effects* / Q000201:enzymology
D018691:Excitatory Amino Acid Antagonists; D018696:Neuroprotective Agents; D004533:Egtazic Acid; D016291:Dizocilpine Maleate; D024442:Aspartate Aminotransferase, Mitochondrial; D015784:Betaxolol; D002118:Calcium