Oxytocin

Oxytocin in the research literature

Oxytocin has a paper trail going back seven decades. Du Vigneaud, Ressler and Trippett, 1953, worked out the order of its nine residues and proposed the ring-and-tail structure: a six-residue ring closed by the Cys1-Cys6 disulphide, and a three-residue tail ending in glycinamide. Vasopressin, made in the same tissue, differs at only positions 3 and 8, and telling the two apart, both chemically and at their receptors, runs through the assay literature ever since.

The receptor work came later. Gimpl and Fahrenholz, 2001, reviewed the oxytocin receptor as a G protein-coupled receptor, covering its structure, its function in cell systems and how its expression is regulated. Jurek and Neumann, 2018, updated that picture with the signalling cascades inside the cell downstream of receptor binding.

For analytical work the disulphide is the point of interest. A reduced or mis-paired bridge changes both mass and HPLC retention, so it is the feature identity methods check first.

Oxytocin: what to check on a research vial

Three things. First, the salt. Research oxytocin is usually supplied as the acetate, which has its own PubChem record and a higher mass than the 1,007.2 Da free peptide; the 5mg on our label is peptide content, and the lab report, once published on this page, will give mass against the free peptide. Second, the units. Licensed oxytocin injection in the UK is labelled in international units per millilitre, while a research vial is labelled by mass, one more way to tell the two apart. Third, the name. Carbetocin is a different, longer-acting analogue, and vasopressin differs at two positions, so a label naming either is not oxytocin. One 5mg size; packs of two, three and five take 10, 20 and 30% off. Oxytocin UK orders leave Manchester the same day, with free UK delivery over £40.