Studies on prolactin 48: isolation and properties of the hormone from horse pituitary glands.

The research article discusses the extraction of a hormone called prolactin from the pituitary gland of a horse, examines its potency, and analyzes its structure, comparing it to that of prolactin from other mammals.

Research Methodology and Findings

• The researchers started by isolating prolactin from the pituitary glands of horses.
• The isolated hormone showed a potency of 42 International Units per milligram when tested in the pigeon crop-sac test. This test is a standard assay for prolactin activity.
• The prolactin hormone was found to be made up of 199 amino acids.

Comparison with Other Mammalian Prolactin

• The structure of the equine prolactin was unique compared to prolactin molecules found in other mammals. Specifically, equine prolactin only contained four half-cystine residues. These residues are typically involved in forming disulfide bonds that stabilize the protein’s structure.
• However, other mammalian prolactins usually have six such residues, suggesting a different structure in the equine prolactin molecule.

Structural Analysis

• The structure of the equine prolactin molecule was further investigated using NH2-terminal sequence analysis and examination of amino acid composition of cyanogen bromide fragments.
• These tests revealed the absence of the NH2-terminal disulfide loop in the equine prolactin, another structural difference from other mammalian prolactins.
• Furthermore, circular dichroism spectra indicated that the alpha-helical content of equine prolactin (a measure of its structural complexity) is lower (50%) than that of prolactin from sheep (65%). This suggests that the equine hormone may have a less complex, and perhaps less stable, structure than the ovine version of the hormone.

Conclusion

• The research provides important insights into the unique properties and structure of equine prolactin. The observed differences in structure could potentially affect how the hormone functions. However, further exploration would be required to understand the full implications of these variations.