Salt Sensitivity and Central Dopaminergic Activity in Patients with Essential Hypertension

: The pathophysiological role of the central dopaminergic mechanism in human essential hypertension (EH) is still unknown. We studied on the relationship between the dopaminergic activity and the salt-sensitivity. Twenty three hospitalized patients with EH were divided into the salt-sensitive group (SS, n = 12) or non salt-sensitive group (NSS, n = 11) by their responses whether they caused more than 8% increase in mean blood pressure (MBP) when the dietary salt was increased from 2g/day to 20g/day for 7 days of each. The change of central dopaminergic activity by the salt load was evaluated by the decrement of plasma prolactin (PRL) response to small dosage (25 micrograms) of thyrotropin releasing hormone. The mean percent change of PRL response by the salt load in the SS group was -6.5 +/- 8.3% (mean +/- SEM), which was significantly lower than 26.8 +/- 5.5% in the NSS group (p less than 0.01). There was a significant negative correlation between the percent changes of PRL response and the percent changes of MBP by the salt load (r = -0.448, p less than 0.05). These results suggested that the rise in blood pressure by salt load in SS patients with EH might be due to a reduced activity of the central dopaminergic mechanism.