Cell swelling, impulse conduction, and cardiac arrhythmias in the failing heart. Opposite effects of angiotensin II and angiotensin (1-7) on cell volume regulation.

The influence of hypotonic solution on cell volume and electrophysiology properties of the failing heart of cardiomyopathic hamsters (TO-2) was investigated. The results showed an increase in cell volume of quiescent isolated ventricular myocytes by 66% within 30 min. Angiotensin (1-7) [Ang (1-7)] (10(-8) M) administered to isotonic solution, elicited a gradual decline in cell volume and a significant decrease of the swelling-activated chloride current (I (Clswell)). The effect of Ang (1-7) on cell volume was inhibited by ouabain (10(-7) M). Angiotensin II (10(-8) M) caused cell swelling and increased I (Clswell). Experiments performed on isolated left ventricles of cardiomyopathic hamsters at an advanced stage of the disease, indicated that hypotonic solution prepared by diluting the normal Krebs solution by 25%, showed a gradual decrease of conduction velocity, generation of early after depolarizations and block of impulse conduction within 10 min. Implications to myocardial ischemia are discussed.