Cardiovascular and lymph flow changes caused by physiological hyperosmolar provocation in unanesthetized rats.

Cardiovascular and thoracic duct lymph (TDL) flow alterations were investigated in non-starved rats, lightly sedated with neuroleptanalgesia, before and after osmolar loading. 0.29-, 1.0- and 2.0-M xylose solutions were infused at the rate of 4 ml X h-1 for 20 min. Neither control animals receiving 0.29-M infusions (iso-osmolar) nor those which received 1- and 2-M infusions showed any detectable changes in cardiac output, heart rate, total peripheral resistance or any organ and tissue flow. On the other hand, TDL flow increased during the hyperosmolar infusions, giving a high degree of correlation with infusion time (r = 0.88 and 0.94, for 1- and 2-M infusions, respectively). These results indicate that hyperosmolar loading has only fluid physiological effects under normotensive conditions.