Effects of intradermal injection of atrial natriuretic peptide.

Atrial natriuretic peptide (ANP) causes mast cell degranulation in rats in vivo and in vitro but is bronchodilator in humans. The aim of this study was to investigate the wheal and flare dose-response to intradermal injection of alpha-human ANP in normal humans. Eight normal subjects received five 30 microliters injections containing 1, 10, 39, 78, 117 pmol ANP and one each of normal saline, histamine 675 pmol and substance P 30 pmol. Maximum ANP flare response was greater but not significantly than that to saline at 1.55 +/- 0.6 (mean +/- s.e. mean) compared with 0.42 +/- 0.17 cm2, but much less than to histamine 9.86 +/- 0.97 or to substance P 12.5 +/- 1.2. Maximum ANP wheal response was significantly greater than that to saline at 0.38 +/- 0.08 compared with 0.18 +/- 0.05 cm2 (difference between means 0.20, 95% CI 0.05, 0.35), but much less than to histamine 0.75 +/- 0.06 or to substance P 1.05 +/- 0.08 cm2. No dose-response to ANP was demonstrated, though responses to the highest dose differed significantly from those to the lowest dose studied. We conclude that human cutaneous responses to ANP differ from those of animals and that the skin is less responsive than other tissues in humans.