INHIBITION OF CONTRACTION OF ISOLATED LYMPHATIC DUCTS BY ATRIAL-NATRIURETIC-PEPTIDE

Atrial natriuretic peptide (ANP) potently relaxes blood vessels but its effect on lymphatic motility is unreported. We studied the effect of ANP, and the smooth muscle relaxing agent nitroprusside (NP), on isolated ovine mesenteric lymphatic ducts. Duct segments were mounted on a myograph, and noncumulative dose-response curves were obtained for the effect of ANP and NP on the rate and force of spontaneous (and norepinephrine-induced) duct contraction. Both ANP (threshold approximately 1 nM) and NP (threshold approximately 10 nM) in a dose-related fashion reduced the frequency and force of contraction of both spontaneously contracting and norepinephrine-stimulated duct segments. ANP may therefore affect interstitial fluid balance through its effect on lymphatic motility.