Key Points
- To evaluate circulating atrial natriuretic factor levels and determine in vitro secretory responses to stretch and adrenergic stimulation in atria from young versus aged rats.
- Measured systolic arterial pressure and right atrial pressure in vivo in young (3 months) and aged (16–24 months) rats.
- Isolated left atria and measured atrial natriuretic factor release in vitro using a perifusion system under basal conditions, mechanical stretch (increased external tension for 20 minutes), and adrenergic stimulation with phenylephrine (10^-5 M for 30 minutes).
- Circulating plasma atrial natriuretic factor levels were significantly higher in aged rats compared to young rats (52 ± 8 vs. 21 ± 6 pmol/l; p < 0.05), despite no difference in right atrial pressure.
- Basal in vitro secretion was significantly elevated in aged versus young atria (875 ± 35 vs. 402 ± 22 pg/min; p < 0.05).
- Adjusted for basal rates, aged atria demonstrated greater secretion in response to phenylephrine (1,687 ± 143 vs. 788 ± 113 pg/min; p < 0.05), while the secretory response to stretch showed a non-significant reduction (673 ± 37 vs. 773 ± 27 pg/min; p = 0.07).
Structured PICO
PPopulationYoung (3 months) and aged (16-24 months) rats
IInterventionAdrenergic stimulation with phenylephrine (10(-5) M) and external stretch in isolated left atria
CComparatorYoung rats (3 months) compared to aged rats (16-24 months)
OOutcomePlasma atrial natriuretic factor levels and atrial natriuretic factor secretion ratesurrogate
Aging in rats is associated with increased basal and adrenergic-stimulated atrial natriuretic factor secretion, which may contribute to the higher plasma levels observed during aging.