Purpose of research product

α-Melanocyte stimulating hormone (α-MSH) is a 13 amino acids peptide with a molecular weight of 1665. The N-terminal serin is acetylated and the C-terminal valine is amidated. The amino acid sequence of α-MSH is identical to ACTH 1-13 in man.

α-MSH is derived from pro-opiomelanocortin, a precursor protein which contains, within its structure, the sequences of other melanotropic peptides like g-, ?-MSH and ACTH.

α-MSH stimulates melanosome dispersion within dermal melanocytes and melanin biosynthesis within epidermal melanocytes.

α-MSH is a potent modulator of fever and inflammation. Plasma α-MSH increases in human subjects with high fever caused by endotoxin administration. The average plasma α-MSH level has been found higher in subjects with AIDS  than in control subjects.

The result shall not be used for clinical diagnosis or patient management.

Technical information

α-MSH is analysed by the competitive radioimmunoassay using an antiserum to an α-MSH-albumin conjugate. α-MSH in standards and samples compete with ¹²⁵I-labelled α-MSH in binding to the antibodies.

¹²⁵I-α-MSH binds in a reverse proportion to the concentration of α-MSH in standards and samples. In order to increase the sensitivity of the assay a sequential assay with delayed addition of ¹²⁵I-α-MSH is performed. Antibody-bound ¹²⁵I-α-MSH is separated from the free fraction using the double antibody polyethylene glycol precipitation technique. The radioactivity of the precipitates is measured. The antiserum used in this kit is directed to the C-terminal part of the a-MSH molecule and shows no crossreactivity with adrenocorticotropic hormone.

Kit components and storage of reagents

The reagents provided in each kit are sufficient for 100 tubes.

1. Anti-α-MSH (Reagent A)

Rabbit antiserum raised against α-MSH conjugated to bovine serum albumin. Lyophilized in 2.0 mL 0.5 M phosphate buffer, pH 7.4, 2.5% human serum albumin, 2.5% EDTA disodium salt, 0.5% sodium azide and 5000 KIU Trasylol^a per mL. For 100 tubes. Reconstitute in 22 mL distilled water.

2. ¹²⁵I-α-MSH (Reagent B)

Contains 0.75 μCi or 28 KBq at reference date. Produced by iodination of synthetic α-MSH. HPLC-purified, monoiodinated. Specific activity: 1700-2100 μCi/nmol (62-77 Mbq/nmol).

Lyophilized in 2.5 mL 0.5 M phosphate buffer, pH 7.4, 2.5% EDTA disodium salt, 0.5% sodium azide and 5000 KIU Trasylol^a per mL. Contains 0.12 mL normal rabbit serum. Reconstitution in 25 mL distilled water.

3. Double antibody-PEG (Reagent C)

50 mL diluted goat anti-rabbit-IG antiserum. 0.05 M phosphate buffer, pH 7.4, with 0.25% human serum albumin, 0.25% EDTA disodium salt and 0.05% sodium azide.

Contains 5.0% w/v polyethylene glycol 6000.

4. Diluent (Reagent D)

25 mL 0.05 M phosphate buffer, pH 7.4, with 0.25% human serum albumin, 0.25% EDTA disodium salt, 0.05% sodium azide and 500 KIU Trasylol^a per mL. To be used for dilution of the α-MSH standard.

5. a-MSH standard, 300 pmol/L (Reagent E)

5.00 mL, 300 pmol/L (500 pg/mL) α-MSH standard. Lyophilized in 0.05 M phosphate buffer, pH 7.4, 0.25% human serum albumin, 0.25% EDTA disodium salt, 0.05% sodium azide and 500 KIU Trasylol^? per mL. Reconstitution in 5.00 mL distilled water.

6. Controls (Reagent F-G)

Lyophilized controls. 1.00 mL of each control after reconstitution. The α-MSH concentrations of the controls are given on the labels of the vials. Contains 0.05% sodium azide.

Reagent preparation and storage

Store all reagents at 2-8° C before reconstitution and use. The water used for reconstitution of lyophilized reagents should be destilled in an all-glass apparatus or be of corresponding purity. Dissolve the contents in a vial by gentle inversion and avoid foaming. The stability of the reagents is found on the label of the vials. For lyophilized reagents the expiry dates are valid for the unreconstituted reagents. Reconstituted reagents are stable for 10 weeks, or until the expiry date is reached, stored correctly.