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 β-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 16weeks 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 4weeks of age, these cells were rarely observed at 8, 12, and 16weeks of age in WKY/Izm. In SHR/Izm, intense DBH immunoreactivity was observed in some glomus cells at 4weeks of age, these cells were also observed at 8 and 12weeks of age, and their number increased at 16weeks of age. An image analysis showed that the percentage of DBH-immunopositive glomus cells in WKY/Izm was approximately 30% at 4weeks of age and significantly decreased to approximately 10% at 8, 12, and 16weeks of age (p<0.05). This percentage in SHR/Izm was approximately 40% at each age. The gray scale intensity for DBH immunoreactivity in DBH-immunopositive glomus cells was similar in both strains at 4weeks 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.