title: Atrial natriuretic factor increases the magnitude of duodenal spontaneous phasic contractions.
abstract: The present investigation was designed to determine if atrial natriuretic factor relaxes non-vascular smooth muscle. Rather than cause a relaxation, atrial natriuretic factor induced a two-to-four fold enhancement in the amplitude of the spontaneous phasic contractions of duodenal longitudinal muscle. Dose-response curves revealed that ANF enhanced these contractions over a concentration range of 10 picomoles to 100 nanomoles with the ED50 at 1 nanomolar. The increased amplitude of contraction began within 30 seconds and was calcium-dependent. The increased force of contraction was associated with a three-fold increase in cyclic GMP levels and activation of particulate guanylate cyclase [E.C.4.5.1.2.]. Atrial natriuretic factor had its half-maximal [ED50] activation of guanylate cyclase at its 1 nM concentration while maximal enhancement was at its 100 nM concentration in duodenum, jejunum, and ileum. Atrial natriuretic factor did not stimulate adenylate cyclase [E.C.4.6.1.1.]. Thus, atrial natriuretic factor increases the force of the spontaneous phasic contractions of the small intestine which are calcium-dependent and associated with activation of the guanylate cyclase-cyclic GMP system.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004386:Duodenum / Q000187:drug effects*; D006162:Guanylate Cyclase / Q000378:metabolism; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains
chemical_list: D009320:Atrial Natriuretic Factor; D000262:Adenylyl Cyclases; D006162:Guanylate Cyclase