Secretion of atrial natriuretic peptide (ANP) from fish atrial and ventricular myocytes in tissue culture

Primary cultures of atrial and ventricular myocytes (approx. 1 x 10(5) cells/culture) were prepared from adult teleost fish Gila atraria and maintained for 10 days. Immunoreactive atrial natriuretic peptide (ir-ANP) from fish atrial and ventricular cells was 3.9 and 2.8 ng/culture respectively, values not significantly different. Atriocytes from rat and mouse secreted comparable amounts of ANP which were not significantly different from atrial fish cultures (5.2 and 4.3 ng/culture). In contrast, their ventricular myocytes secreted only small quantities of ANP (0.8 and 0.3 ng/culture). When analyzed by reversed-phase HPLC, the media of both fish atrial and ventricular myocytes contained a peptide which exhibited properties similar to authentic human ANP (Ser 99-Tyr 126), suggesting a significant degree of sequence homology between fish and mammalian ANP. Fish ventricular cells, unlike normal mammalian ventricular cells, secrete substantial quantities of immunoreactive-ANP.