Effects of obstruction of the mitral orifice or distention of the pulmonary vein--atrial junctions on renal and hind-limb vascular resistance in the dog.

This investigation attempted to determine whether stimulation of intrathoracic receptors, including those in the left atrium, is associated with changes in renal vascular resistance. In 19 dogs, the left kidney was perfused at constant pressure and the right hind limb was perfused at constant flow. A partial obstruction of the mitral orifice that increased left atrial pressure by less than 20 cm H,0 caused tachycardia, hypotension, renal vasodilatation (5% increase in flow), and hind-limb vasoconstriction (10% increase in pressure). A partial obstruction of the orifice that raised left atrial pressure more than 20 cm H,0 caused tachycardia, hypotension, and more hind-limb vasoconstriction (20% increase in pressure), but renal vascular resistance did not change. After bilateral vagotomy in either the thorax or the neck, partial obstruction of the mitral orifice caused constriction in both the renal and the hind-limb vascular beds. In 10 dogs, localized distention of three pulmonary vein-left atrial junctions caused an increase in heart rate and a small but significant increase in renal blood flow but had no effect on hind-limb vascular resistance. At least a part of the reflex renal dilatation caused by mitral obstruction probably resulted from stimulation of left atrial receptors.