Dissociation of Insulin Absorption and Blood Flow During Massage of a Subcutaneous Injection Site

Nine healthy volunteers with normal body weights were injected subcutaneously with ¹²⁵I-labeled soluble human insulin (10 U) in one thigh and ¹³³Xe in the contralateral thigh for the measurement of subcutaneous blood flow on 2 consecutive mornings. On one of the days, standardized massage of both injection sites was performed for 30 min starting 30 min after insulin injection. Serum insulin and plasma glucose were determined intermittently before, during, and after massage, and elimination of radioactivities was monitored continuously by external detectors. During massage, the first-order elimination rate constants of ^l25I increased approximately sixfold compared with the rise during control (0.19 ± 0.04 to 0.88 ± 0.15%/min during the last 15 min of the massage vs. 0.21 ± 0.03 to 0.32 ± 0.03%/min during control). Serum insulin increased from 13.8 ± 1.8 mU/L before massage to a maximal value of 56.4 ± 8.7 mU/L 10 min after massage (vs. 15.3 ± 3.0 and 19.7 ± 2.2 mU/L during control). Plasma glucose fell significantly faster on the massage day, from 10 min after massage onward. No significant alteration in the subcutaneous blood flow was found during or after massage. The results suggest that the pronounced enhancement of insulin absorption induced by massage of the injection site is mainly not blood flow mediated.