Purchase this article with an account.
S. Bose, K. Rarey, I. Bettahi, C. Kenney, N. Morishige, K. Waymire, D. Wallace, J.V. Jester; Mitochondrial Abnormalities in Extraocular Muscles of Hyperthyroid Adenosine Nucleotide Translocator–1 (ANT1) Deficient Mice . Invest. Ophthalmol. Vis. Sci. 2006;47(13):5401.
Download citation file:
© ARVO (1962-2015); The Authors (2016-present)
Since mitochondria, the major site of oxidative phosphorylation in the cell, are considered a likely target for the action of 3,3’,5 Triiodo–L–Thyronine (T3), it is hypothesized that T3–induced hyperthyroidism might result in a reduction of mitochondrial energy with or without structural alteration in the extraocular muscles (EOMs) in ANT1 deficient mice. The ANT1 gene encodes an inner mitochondrial membrane protein that transports ATP into the cell and the ANT1–/– mutant develops mitochondrial limb myopathy. The study aims to determine if hyperthyroid mutant mice differing in mitochondrial metabolism also differ in ultrastructural alterations of EOMs when compared to hyperthyroid controls.
T3 hyperthyroidism was induced in 8–12 weeks old ANT1 mutant mice using 5µg/100g body weight T3 (pH 9.2) by intraperitoneal injections daily for 4 weeks (n=8). At 4 weeks post treatment, animals were euthanized; blood collected for measurement of T3, TSH levels. EOMs were also removed and evaluated by light and transmission electron microscopy (TEM). Selected samples were stained by mitotracker (Molecular probes) and evaluated by two–photon excited fluorescence (TPEF) and second harmonic image microscopy (SHIM) to provide spatial information concerning actinomysin mitochondrial localization. Results were compared with the control group that received injections of normal saline at the same pH (n=10).
T3 and TSH levels in hyperthyroid ANT1 mice (mean 462±50 ng/dl; <0.01 µIU/ml) vs. control mice (182±45; 0.2±0.01) confirmed hyperthyroidism (p<0.01). In contrast to controls, the EOMs of hyperthyroid ANT1 mice demonstrated interstitial edema with no cellular infiltration, numerous elongated abnormal looking mitochondria and distortion of normal sarcomeric organization. TPEF and SHIM showed similar changes with marked increase in mitochondrial density and loss of sarcomeric SHG signal generation from the A–band of the EOM, confirming the TEM results in the mutant ANT1 mice.
EOM abnormalities in the hyperthyroid ANT1 deficient mouse suggest that mitochondria may play a significant role in the pathogenesis of hyperthyroid eye disease; these studies will allow us to determine the possible sites of mitochondrial derangement that may help in developing treatment strategies.
This PDF is available to Subscribers Only