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Updated: May 19, 2026
A Suction Blister Protocol to Study Human T-cell Recall Responses In Vivo
Published on: August 11, 2018
Interstitial fluid contains higher in vitro IGF bioactivity than serum: a study utilizing the suction blister
Ulrick Espelund1, Klaus Søndergaard, Peter Bjerring
1Department of Endocrinology and Internal Medicine, Aarhus University Hospital, Denmark. uespelund@hotmail.com
Context:
Circulating insulin-like growth factors (IGFs) are bound in complexes which affect their tissue-accessibility. Interstitial fluid is in close proximity to target cells, but the IGF-system is not well-described herein.
Objective:
To perform a thorough comparison of the IGF-system in suction blister fluid (SBF) vs. in serum, with emphasis on bioactive IGF levels.
Design:
Eight hour study including samples collected in the fasting state (20 h) and after a meal.
Setting:
Clinical research facility.
Participants:
Six healthy males (age 37.0±8.8 years, BMI 22.5±1.4 kg/m(2)) (mean±SD).
Main Outcome Measure:
Serum and SBF concentrations of bioactive IGF (determined in vitro by specific IGF-I receptor (IGF-IR) phosphorylation assay), immunoreactive IGF and IGF binding protein (IGFBP) levels, Western ligand blotting (WLB) of IGFBPs and IGFBP-3 Western immunoblotting (WiB).
Results:
The ability of SBF to phosphorylate the IGF-IR in vitro was 41±27% higher than that of serum (P=0.007 by repeated measures ANOVA). By contrast, immunoreactive IGF and IGFBP-concentrations were approximately 50% lower in SBF than in serum (all P≤0.002). A marked difference in the composition of IGFBPs between serum and SBF was observed, including 3-fold elevated amounts of IGFBP-3 fragments in SBF (P<0.001). For both IGF-I, IGF-II and IGFBP-2, the effect of food intake differed between serum and SBF (all P≤0.03).
Conclusion:
Despite lower concentrations, the in vitro IGF bioactivity was higher in SBF than in serum. This may relate to an increased enzymatic IGFBP-degradation and an altered IGFBP-composition in SBF, making more IGF-I and -II accessible to the IGF-IR. The impact of food intake on the IGF system differs between serum and interstitial fluid.
