Distribution and physiological function of atrial natriuretic peptide.

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1. Phylogeny of atrial natriuretic peptide (ANP). In the representative animals of all vertebrate classes, atrial and ventricular cardiocytes retain secretory granules. The granules, except those of Aves, are immunoreactive against anti-human ANP (HANP) antiserum.2. ANP in Fishes. (1) In thirteen species from cyclostomes, cartilagenous fishes and teleosts, the immunoreactive ANP in the atrial and ventricular extracts and plasma was estimated by radioimmunoassay. There was no difference in these values between freshwater and seawater fishes. (2) Chromatographic analysis of carp atrial and ventricular extracts indicated that the major component of immunoreactive ANP is a peptide with high molecular weight (about 12.5 KD), being regarded as gamma-ANP. The two minor components were coeluted with beta-hANP (6 KD) and alpha-hANP (3 KD). (3) The atrial extracts showed a vasodepressor activity in the quail, and the activity was diminished after incubation of extracts with anti-hANP antiserum.3 … More . ANP in Amphibia and Reptile. (1) In Japanese toad, African clawed-toed toad and soft-shelled turtle, the ANP immunoreactive secretory granules is first noted in the atrial and ventricular cardiocytes, when the heart begin to beat. Then, the number of the granules increases gradually in the latter two species, but abruptly, in the toad, before the metamorphosis is completed. (2) Effects of hypophysectomy and thyroidectomy on ANP immunoreactivity. Neither hypophysis nor thyroid may be essential for ANP synthesis in larval hearts but thyroid hormones may possibly modulate synthesis and/or release of ANP from the cardiocytes. (3) The cardiocytes in the atrium and ventricle of the spring (breeding) toads had larger nuclei and showed stronger ANP immunoreactivity than those of the summer (non-breeding) toads. Plasma levels of immunoreactive ANP were also higher in the spring than summer toads. Whether ANP serves a physiological roles in regulation of water and sodium balance in temporary aquatic life during the breeding season is not clear at present. Less