Orthostatic changes in subcutaneous blood flow and insulin absorption.

Subcutaneous blood flow (SBF), measured by the 133Xenon local clearance technique, and absorption of subcutaneously injected 125I-labelled short-acting insulin from the femoral and abdominal regions were studied in 17 diabetic patients during supine and sitting position. Sitting up induced vasoconstriction with a 28.7-47.0% fall in SBF and a 19.2-43.6% fall in the insulin absorption rate. These findings imply that the SBF of the thighs and abdomen participate in the cardiovascular adjustments to postural changes. The change in the insulin absorption rate during the change of position probably contributes to the great day-to-day variation of insulin absorption. Furthermore, the observation stresses the importance of well defined experimental conditions in insulin absorption studies.