Chronotropic and inotropic effects of hyperosmotic solutions on right and left atria isolated from the rat heart

The chronotropic and inotropic effects of hyperosmotic solutions (HS) on isolated rat atria were studied to determine the influences of solute, time and blockade of autonomic receptors. NaCl and sucrose HS (450 mOsm/1) exerted a time-dependent negative chronotropic effect on right atria. NaCl decreased whereas sucrose increased peak tension of the left atria. Phenoxybenzamine and propranolol did not change the chronotropic effects of hyperosmolality, but increased the peak tension of left atria exposed to HS. We conclude that chronotropic effects of HS seem to be non-specific while inotropic effects depend on the solute and may involve neurotransmitter release, probably acetylcholine.