Hemodynamic and hormonal responses to bolus intravenous injections of synthetic porcine endothelin (pET) were examined in anesthetized dogs. There were no significant changes in mean blood pressure (MBP), right atrial pressure (RAP), or plasma atrial natriuretic factor (ANF) concentration in response to 40 pmol/kg of the peptide. However, responses to 400 pmol/kg of the peptide were significant: MBP rose from 114 +/- 6 mmHg (mean +/- SE) to 139 +/- 7 mmHg (p less than 0.01), RAP rose from 5.4 +/- 0.9 mmHg to 7.8 +/- 1.1 mmHg (p less than 0.01), and ANF increased from 45 +/- 10 pg/ml to 277 +/- 33 pg/ml (p less than 0.01). Peak value of RAP was observed 2.6 +/- 0.4 min, while peak of ANF was 11.4 +/- 0.9 min after peptide injection. There was a strongly positive correlation (r = 0.93, p less than 0.01) between the increase in RAP and the increase in ANF in dogs given 400 pmol/kg of pET. These results indicate that exogenously administered pET to anesthetized dogs alters hemodynamics and induces ANP release, and are compatible with a postulate that the ANF release is caused by elevated RAP.