EFFECTS OF SUBCUTANEOUS INSULIN-LIKE GROWTH-FACTOR-I INFUSION ON SKIN MICROCIRCULATION

When healthy volunteers were treated with human insulin-like growth factor-I (IGF-I), mild generalized edema often developed. In the present study, the effect of IGF-I on cutaneous capillary permeability and microvascular skin blood flow was investigated using fluorescence videomicroscopy and laser Doppler fluxmetry. Transcapillary diffusion of intravenously injected sodium fluorescein (NaF) was quantitated by videodensitometry in terms of fluorescent light intensities (FLIs) 5, 10, 20, 30, 60, 120, 180 and 300 s after the first appearance of the dye. Laser Doppler fluxmetry was performed at rest (LDF(rest)) and during postocclusive reactive hyperemia (LDF(peak)). Eight healthy subjects (3 women, 5 men; mean age 28 years, range 24-30 years) were investigated. The sensing site was the skin on the right dorsal wrist. Measurements were performed after 4 days of subcutaneous infusion of 0.9% saline (control) and of IGF-I. Mean values for the FLI were significantly higher after IGF-I than after saline infusion (p < 0.05), when the FLIs were expressed in arbitrary units. As percentages of their individual maxima, the differences were significant (p = 0.05) after 60 s (23.6 +/- 6.6% with NaCl and 31.9 +/- 7.6% with IGF-I). LDF(rest) and LDF(peak) tended to be higher after IGF-I treatment without achieving statistical significance (p = 0.176). The mean appearance time of the dye after injection was significantly shorter (p = 0.016) in the IGF-I group than in the control group (32.0 +/- 8.4 s with IGF-I, 42.4 +/- 8.3 s with NaCl). In conclusion, IGF-I does not increase skin blood flow, but significantly increases transcapillary diffusion of NaF. Both mechanisms may be responsible for the development of edema.