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ABSTRACT: Long-term hypoxia (days to weeks) increases phosphorylation of tyrosine hydroxylase (TH) at Ser31 and Ser40 in the carotid body (CB). In the present study, we examined the time course of TH phosphorylation at Ser31 and Ser40 in CB of rats exposed to short-term hypoxia (within 1 day) for 0-24h. Using immunoblotting, the signal intensities of both phosphorylated TH were more intense in CB of rats exposed to hypoxia for 6, 12, 18, and 24h than those of controls. Using immunohistochemistry, immunoreactive intensities of both phosphorylated TH were significantly more intense in glomus cells after rats were exposed to hypoxia for 6, 12, 18, and 24h than those of controls (p<0.05). These results show that phosphorylation of TH at Ser31 and Ser40 is increased in CB glomus cells by short-term hypoxia, suggesting that activation of TH via phosphorylation contributes to the facilitation of catecholamine biosynthesis in CB glomus cells at an early stage of hypoxia.
Respiratory Physiology & Neurobiology 11/2012; · 2.24 Impact Factor
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Journal of Histochemistry and Cytochemistry 09/2012; · 2.72 Impact Factor
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ABSTRACT: Under hypertension, it has been reported that the carotid body (CB) is enlarged and noradrenaline (NA) content in CB is increased. Therefore, it is hypothesized that morphological and neurochemical changes in CB are induced in hypertensive animal models. In the present study, we examined the morphological features and dopamine β-hydroxylase (DBH) immunoreactivity in CB of spontaneously hypertensive rats (SHR/Izm) and Wistar Kyoto rats (WKY/Izm). The CB of SHR/Izm was elongated in terms of the cross section of center and was enlarged in the reconstructed images compared with that of WKY/Izm, and the total volume of CB in SHR/Izm (0.048 ± 0.004 mm³) was significantly (p<0.05) increased compared with the value in WKY/Izm (0.032 ± 0.006 mm³). By immunohistochemistry, immunoreactivity for tyrosine hydroxylase in CB was mainly observed in glomus cells and the immunostaining properties were similar between WKY/Izm and SHR/Izm. On the other hand, DBH immunoreactivity was mainly observed in nerve fibers around blood vessels and observed in a few glomus cells in CB of WKY/Izm. The number of glomus cells with strong DBH immunoreactivity was increased in SHR/Izm compared with that in WKY/Izm. In conclusion, the present study exhibited the enlargement of CB as three-dimensional image and revealed the enhanced immunoreactivity for DBH of glomus cells in SHR/Izm. These results suggest that the morphology of CB is affected by the effect of sympathetic nerve and that the signal transduction from CB is regulated by NA in glomus cells under hypertensive conditions.
Autonomic neuroscience: basic & clinical 04/2012; 169(1):49-55. · 1.82 Impact Factor
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ABSTRACT: Neurochemical and morphological changes in the carotid body are induced by chronic hypoxia, leading to regulation of ventilation. In this study, we examined the time courses of changes in immunohistochemical intensity for tyrosine hydroxylase (TH) and cellular volume of glomus cells in rats exposed to hypoxia (10% O(2)) for up to 24 hr. Grayscale intensity for TH immunofluorescence was significantly increased in rats exposed to hypoxia for 12, 18, and 24 hr compared with control rats (p<0.05). The transectional area of glomus cells was not significantly different between experimental groups. The TH fluorescence intensity of the glomus cells exhibited a strong negative correlation with the transectional area in control rats (Spearman's rho = -0.70). This correlation coefficient decreased with exposure time, and it was lowest for the rats exposed to hypoxia for 18 hr (rho = -0.18). The histogram of TH fluorescence intensity showed a single peak in control rats. The peaks were gradually shifted to the right and became less pronounced in hypoxia-exposed rats, suggesting that a hypoxia-induced increase in TH immunoreactivity occurred uniformly in glomus cells. In conclusion, this study demonstrates that short-term hypoxia induces an increase in TH protein expression in rat carotid body glomus cells.
Journal of Histochemistry and Cytochemistry 09/2010; 58(9):839-46. · 2.72 Impact Factor
