Measurement of insulin sensitivity: Influence of potassium supply during euglycaemic glucose clamps in healthy volunteers

Insulin sensitivity can be quantitatively measured by the hyperinsulinaemic euglycaemic glucose clamp technique. Infusion of insulin during the clamp procedure leads to a decline of kalaemia unless potassium is supplied. We i nvestigated whether supplementation of potassium during euglycaemic glucose clamps influences insulin sensitivity. In a randomised study the insulin s ensitivity index (SI) was determined with two-step hyperinsulinaemic (insul in infusion rates 0.25 (step 1) and 1.0 mU kg(-1) min(-1) (step 2)) euglyca emic (5.0 mmol L-1) glucose clamps in 20 healthy male volunteers on two dif ferent study days. On one day blood potassium was kept constant by means of a variable i.v. potassium chloride infusion ("eukalaemic potassium clamp") , whereas on the other day the decline in blood potassium was monitored onl y. Without potassium supply kalaemia decreased from basal levels of 4.35 +/ - 0.18 mval L-1 to 4.25 +/- 0.17 (step 1) and further to 3.88 +/- 0.14 mval L-1 (step 2 (mean +/- SD)). Without and with potassium supply the insulin sensitivity index measured was comparable (SI 10.6 +/- 3.6 vs. 9.5 +/- 3.5 ml min(-1) m(2) per mu U ml(-1), n.s.; glucose infusion rates 3.6 +/- 1.6/1 2.6 +/- 2.6 (step 1/step 2) vs. 3.7 +/- 1.5/12.2 +/- 2.7 mg kg(-1) min(-1), n.s.). In conclusion, this study shows that potassium supply during hyperi nsulinaemic euglycaemic glucose clamps in healthy subjects does not influen ce the insulin sensitivity index.