CLINICALLY IMPORTANT DIFFERENCES IN INSULIN ABSORPTION FROM ABDOMEN IN IDDM

The absorption of radiolabeled soluble insulin ([I-125]Actrapid(R) Hum an; 10 U) from subcutaneous injection sites above (120 mm) and below ( 40 mm) the umbilicus was studied on 2 consecutive days in nine IDDM pa tients during 180 min. Insulin absorption was measured as disappearanc e of radioactivity by continuous external monitoring and as appearance of plasma immunoreactive free insulin (IRI). Adipose tissue blood flo w (ATBF) was measured concomitantly by the Xe-133-washout technique. P lasma glucose was determined. Prior to the injections the depth of the subcutaneous fat tissue was determined using ultrasound. Significantl y less radioactivity remained at the upper site, 42 +/- 5 vs. 60 +/- 6 % after 180 min (P < 0.001). In accordance with this, injection into t he site above vs. below the umbilicus resulted in a greater area;under curve for plasma insulin, 3306 +/- 493 vs. 2357 +/- 466 mU/l per min (0-180 min; P < 0.01), and a more pronounced plasma glucose-lowering e ffect (P < 0.05). However, ATBF did not differ significantly between t he two sites. These data suggest that there are clinically relevant di fferences in insulin absorption within the abdomen. Thus, insulin inje ction into the epigastric area causes more rapid insulin absorption re sulting in an enhanced plasma glucose-lowering effect than injection i nto the more conventional site close beneath the umbilicus.