Left atrial pressure and postprandial diuresis in conscious dogs on a high sodium intake

5 conscious, well trained, female dogs kept on a high sodium intake (14 meq Na/kg bw) were used to measure left atrial pressure (LAP), urine volume (V), sodium and potassium excretion (UNaV, UKV) as well as plasma osmolality (Posm) before and up to 180 min after food intake. The dogs were fitted with a catheter in the left atrium (thoracotomy). In all experiments (n=23) LAP increased postprandially (pp) above fasting controls. The mean peak increase ranged from 4 to 6 cm H2O and was observed as early as 61-80 and as late as 161-180 min pp. Increase in LAP was closely correlated to V which rose from 36+28 to 160+51/ul/min. kg. pp V was also correlated to pp UNa V, which increased from 4.8 +/- 3.3 to 34.O+/-8.5/ueq/min-kg. The pp increase in LAP and its close relation to pp V and pp UNav emphasize the assumption that intrathoracic receptors are involved in the regulation of body fluids.