Prostaglandins and Systolic Blood Pressure, but Not Angiotensin Ii, Independently Affect Atrial Natriuretic Peptide Levels in Man

Abstract

1. Two hours after a single dose of indomethacin (INDO), plasma renin activity (PRA) and atrial natriuretic peptide (ANP) levels decreased, which is consistent with an effect of lowering prostaglandins (PG). 2. After 48 h of INDO, PRA remained low but ANP had increased, which is consistent with the known effect of prostaglandin inhibitors to cause sodium retention, with a resulting volume expansion. 3. Infusions of angiotension II (AII), which raises diastolic blood pressure (BP) 20 mmHg or more, consistently raised ANP levels. The ANP response to AII infusion was reduced 48 h after INDO, which is consistent with an important role for PG in AII-stimulated ANP release. 4. After PG were blocked with INDO, the stimulating effect of AII on ANP at doses that increased diastolic BP less than 20 mmHg was insignificant, whereas before INDO it was significant. 5. In dose-response studies, INDO increased the systolic BP response but decreased the ANP response to AII, which is consistent with a direct effect of PG on ANP that is independent of systolic BP. 6. Prostaglandins and BP are important in the ANP response to AII infusion in normal subjects, but AII itself appears to have little direct effect on ANP.

Ageing and Blood Pressure Regulation: Dose‐response Relationships for Angiotensin, Blood Pressure, Atrial Natriuretic Peptide and Aldosterone in Normal Subjects of Varying Ages

“…Whereas a significant change in the present study was not found, such a fall in responsiveness would explain the negative correlation between aldosterone and age in the absence of a negative correlation between PRA and age. The stimulation of ANP by A11 in the present study can be explained by a direct effect of blood pressure rise (Burnett et al 1989) on ANP (supported by the correlation between ANP slope and pressor slope) and by an effect of A11 on ANP mediated by prostaglandins (Klemm et al 1992). There was no apparent effect of age on basal ANP or on the ANP response to AIL Our own unpublished observations (1992) in 260 subjects aged 1-77 years and those of McKnight et al (1989) suggest that ANP changes little with age until after 70 years of age, when levels rise.…”