Effect Of Hyperosmolality On The Sensitivity Of Right And Left Atria Of The Rat To Noradrenaline.

Abstract

This study analyzes the effects of hyperosmotic solutions on the sensitivity of the rat isolated right and left atria to the chronotropic and inotropic effects of noradrenaline (NA), respectively. Hyperosmotic NaCl solution caused subsensitivity to both effects of NA (pD2 values for NA, right atria: control 7.42 +/- 0.06, NaCl 6.83 +/- 0.18, P less than 0.05; left atria: control 7.67 +/- 0.22, NaCl 6.61 +/- 0.18, P less than 0.05). Hyperosmotic sucrose solution produced a similar effect in right atria (pD2 NA: 6.96 +/- 0.17, P less than 0.05), whereas in left atria it depressed the maximum inotropic response to NA by about 80%. All changes, except that of maximum inotropic response, were abolished following combined pretreatment with 6-hydroxydopamine, phenoxybenzamine, atropine and imipramine. These data suggest that the noradrenergic subsensitivity induced in atrial tissue by hyperosmolality is probably not due to changes of beta-adrenoceptor function and/or coupling of these receptors to the effector mechanisms.2281005100