Age-related changes in immunoreactivity for dopamine β-hydroxylase in carotid body glomus cells in spontaneously hypertensive rats

The purpose of this study was to investigate immunoreactivity for dopamine beta-hydroxylase (DBH) and tyrosine hydroxylase (TH) in carotid body (CB) glomus cells in spontaneously hypertensive rats (SHR/Izm) at 4 (prehypertensive stage), 8 (early stage of developmental hypertension), 12 (later stage of developmental hypertension), and 16 weeks of age (established hypertensive stage). Age-matched Wistar Kyoto rats (WKY/Izm) were used as controls. Staining properties for TH were similar between both strains at each age. Regarding DBH immunostaining, although some glomus cells showed intense DBH immunoreactivity at 4 weeks of age, these cells were rarely observed at 8, 12, and 16 weeks of age in WKY/Izm. In SHR/Izm, intense DBH immunoreactivity was observed in some glomus cells at 4 weeks of age, these cells were also observed at 8 and 12 weeks of age, and their number increased at 16 weeks of age. An image analysis showed that the percentage of DBH-immunopositive glomus cells in WKY/Izm was approximately 30% at 4 weeks of age and significantly decreased to approximately 10% at 8, 12, and 16 weeks of age (p < 0.05). This percentage in SHR/Izm was approximately 40% at each age. The gray scale intensity for DBH immunoreactivity in DBHimmunopositive glomus cells was similar in both strains at 4 weeks of age, but became significantly lower in WKY/Izm and higher in SHR/Izm with increase in age (p < 0.05). These results suggest that noradrenaline in glomus cells plays an important role in the regulation of neurotransmission between CB and afferent nerves during developmental hypertension.