IGF-1 direct (Rat, Mouse) ELISA

• is suited for IGF-I determination in serum and plasma of mice and rats
• high sensitive: 0.029 ng/ml analytical sensitivity; required sample volume is very small
• is fast: incubation time a total of 2 hours
• Single Standards with 0.5, 2.5, 6, 12, 18 ng/ml recombinant IGF-I are provided in the Kit
• 2 Control Sera are provided for quality control
• uses high affinity antibodies against m/r IGF-I
• Microtiter plates are separately breakapart

Intended Use

Measurement of IGF-I in mouse / rat serum and plasma.

Beside different cell culture models and studies with human patients, mice and rats are suitable model organisms for basic research and pre-clinical studies.Thus, we developed this test system as a tool for IGF-I measurements in mice and rat for usage in research and preclinical studies. Even if the comparability of mice and humans is limited we offer some background information on the human IGF-I system in the following section:

Insulin-like growth factors (IGF) I and II play a pivotal role in regulating the proliferation and differentiation of many cell types. IGF-I is identical with Somatomedin C (Sm-C) and has a molecular weight of 7649 daltons. Its major regulators are growth hormone (GH) and nutrition (6). In contrast to many other peptide hormones, IGFs are avidly bound to specific binding proteins (IGFBP). The seven IGFBPs which are known at present either bind IGF-I and IGF-II with similar affinities or show a preference for IGF-II.

A major problem of IGF-I measurement results from the interference of IGFBPs in the assay. Direct determinations in untreated serum samples give false values because of the extremely slow dissociation of the IGF-I/IGFBP-3 complexes during the assay incubation. Depending on the ratio IGF-I to IGFBP in the sample interference comes up.

Therefore, various techniques were applied to physically separate IGF-I from its binding proteins before measurement, including (a) size exclusion chromatography under acidic conditions, (b) solid-phase extraction and (c) acid-ethanol extraction. These techniques, however, are either inconvenient or time-consuming or give incomplete and notreproducible recoveries. The most widely used method is the acid-ethanol extraction with a recovery of only 70-80 % of IGFBP-bound IGF-I as a result of co-precipitation. The absolute results of such an extraction are therefore false low. The extraction removes the IGFBPs only insufficiently and leads to reduction in sensitivity of the assay due to predilution of the samples by the extraction procedure. Furthermore, the remaining IGFBP may still interfere in the assay. In addition, the acid-ethanol extraction is ineffective in specimens other than serum or plasma (e.g. cell culture media), in which determination of IGF-I is already difficult enough due to the fact that IGFBPs are frequently present at large excess.

To avoid these difficulties, an uncomplicated assay was developed, in which special sample preparation is not required before measurement.