INFLUENCE OF INTRAOSSEOUS INFUSION OF A SMALL-VOLUME OF HYPEROSMOTIC FLUID ON BETA-ADRENERGIC FUNCTION IN CIRCULATING LYMPHOCYTES FROM BLEDPIGS

The regulation of beta-adrenergic function in circulating mononuclear leukocytes was evaluated during an episode of haemorrhagic shock treat ed by intra-osseous infusion of a small volume of hyperosmotic fluid. Two groups of piglets (n=14) were anaesthetized with ketamine and bled to a mean arterial pressure of 40 mmHg. After 45 min the animals were randomized to receive 100 ml of either hyperosmotic (2.4 mol l(-1)) o r iso-osmotic (0.29 mol l(-1)) fluid (equal volumes of glucose/sodium chloride) into the tibial bone marrow. Observations of haemodynamic va riables and levels of plasma catecholamines and cAMP of circulating mo nonuclear leukocytes were carried out for 70 min. Infusion of hyperosm otic fluid enhanced the circulatory performance and attenuated the pla sma catecholamine release significantly (p < 0.05) compared to the cor responding values in the animals that had iso-osmotic fluid infusion. Measurements of unstimulated and isoprenaline-stimulated cAMP levels i n mononuclear lymphocytes indicated that the high plasma catecholamine levels in the iso-osmotic treatment group induced a desensitization o f the beta-adrenoceptors 70 min after initiation of the shock. This ef fect was not seen in animals that had undergone hyperosmotic infusion.