PLASMA-INSULIN CONCENTRATIONS DURING INFUSION OF POTASSIUM AND SODIUM-CHLORIDE SOLUTIONS INTO CONSCIOUS SPLENECTOMIZED SHEEP

Hematocrit values, plasma osmolality and the plasma concentrations of Na, K, Cl- and insulin were measured in carotid arterial blood before, during and after i.v. infusion of NaCl (0.5 mol l-1) and KCl (0.5 mol l-1) at 2 ml min-1 for 105 min into 6 conscious splenectomized sheep. Hypertonic NaCl infusion was associated with a fall in hematocrit of 1.30 .+-. 0.10% (P < 0.001) and no consistent change in plasma insulin concentration occurred during this infusion. Hypertonic KCl infusion caused the hematocrit to increase by 1.70 .+-. 0.39% (P < 0.001) and the plasma insulin concentration to increase by 60.0 .+-. 16.3 .mu.U ml-1 (P < 0.01). This increase in insulin concentration was caused by elevation of the plasma K concentration and was not due to coincident increases in plasma chloride concentration or osmolality. Shrinkage of the extracellular fluid volume during KCl infusion made no major contribution to the increase in insulin concentration which was probably the result of increased release from the pancreas.