Comparison of cyclic guanosine monophosphate response to infusion of atrial natriuretic peptide in young and elderly subjects.

OBJECTIVE

To compare the sensitivity to atrial natriuretic peptide (ANP) in young and elderly subjects.

DESIGN

Double-blind, random-order, placebo-controlled study using two different rates of ANP infusion.

SUBJECTS

Eight healthy young (23 +/- 3 years, mean +/- SD) and eight healthy elderly (76 +/- 4 years) subjects recruited from the general population.

MEASUREMENT

Plasma cyclic guanosine monophosphate (cGMP, the second messenger of ANP) levels reflecting the sensitivity of biologically active ANP receptors.

RESULTS

Baseline ANP levels were higher and rose to a greater extent in the elderly both during low- (0.25 microgram/min) and high-dose (2.0 micrograms/min) infusion of ANP. Plasma levels of cGMP rose in proportion to the increase in ANP. When the rise in cGMP levels was related to the increase in ANP levels (expressed as nmol/L per 100 pg/mL ANP increase), no difference was found between young and elderly subjects.

CONCLUSION

The ability of elderly subjects to increase cGMP in response to exogenous ANP is similar to that of young subjects. This may reflect a similar sensitivity of the target organs towards ANP. However, because of lower clearance in the elderly, a similar dose of ANP results in a greater elevation of ANP and cGMP levels and hence induces a greater effect.