Filtration pressure response to infusion of atrial natriuretic peptides

The present experiments were undertaken to assess the effect of an atrial extract (ANF) and of the synthetic atriopeptin II (APII) on filtration pressure of rat kidneys. Continuous recordings of stop flow pressure (SFP) were made to obtain an index of the change of glomerular capillary pressure produced by atrial peptides and its time course. Short-term infusion of ANF or APII increased SFP from 40.6 +/- 0.99 to 50.7 +/- 1.42 mm Hg (p less than 0.001) and from 44.0 +/- 1.28 to 52.7 +/- 1.75 mm Hg (p less than 0.001) respectively. The maximum response was achieved promptly. Return of SFP to control was slow: 20 minutes after termination of the infusion SFP was still elevated by 4.9 +/- 1.27 mm Hg (p less than 0.01). Tubule and stellate vessel pressures increased less than 2mm Hg, changes that were not significant. Arterial pressure fell 6 mm Hg (p less than 0.05). When arterial pressure was reduced by an aortic clamp to 85-90 mmHg prior to administration of APII the response of SFP was markedly blunted (from a mean increase of 9.0 +/- 1.07 mm Hg to 4.5 +/- 0.53 mm Hg). The increase of SFP probably reflects an increase of glomerular capillary pressure. The finding suggests that atrial peptides increase glomerular filtration rate at least in part by increasing filtration pressure.