INTERACTION BETWEEN STRETCH AND HORMONALLY STIMULATED ATRIAL-NATRIURETIC-PEPTIDE SECRETION

Atrial stretch and paracrine hormones stimulate atrial natriuretic peptide (ANP) secretion. The potential interplay between atrial stretch and paracrine hormones was examined. Isolated superfused rat left atria paced at 4 Hz were used for study. The effects of 0, 0.5, and 1.5 g settings of initial tension on the ANP secretory response to 1-mu-M norepinephrine and 10 nM endothelin were examined. The peak ANP secretory responses expressed as a percent of baseline for each of the tension settings were 109 +/- 8, 132 +/- 6, and 171 +/- 10% for norepinephrine and 285 +/- 15, 294 +/- 12, and 368 +/- 19 for endothelin, respectively. The effects of 0.5-mu-M norepinephrine, 1 nM endothelin, and 100 nM vasopressin on stretch-stimulated secretion were examined. Norepinephrine and endothelin increased ANP secretion 144 +/- 16 and 136 +/- 2% above baseline, respectively. Vasopressin did not increase ANP secretion. Norepinephrine and vasopressin did not significantly influence the ANP secretory response to stretch. In contrast, endothelin increased the response to stretch by 33% (P < 0.035). We conclude 1) the greater the degree of atrial stretch, the greater is the response to norepinephrine and endothelin; 2) endothelin enhances the secretory response to stretch; and 3) norepinephrine and vasopressin do not affect stretch-stimulated release. These results predict a greater ANP secretory response to hormonal stimulation in vivo in volume-expanded states.