Increased total volume and dopamine β-hydroxylase immunoreactivity of carotid body in spontaneously hypertensive rats

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.