Preparation and properties of growth hormone from equine pituitary glands.

This research paper discusses how growth hormone from horse pituitary glands was prepared and analyzed, finding that it contains significant prolactin activity but little to no ACTH, TSH, and gonadotropic activity.

Research Design and Procedures

• The researchers first prepared equine growth hormone from acetone-dried residues. These residues were obtained after extracting gonadotropins from fresh, frozen horse pituitary glands.
• The growth hormone was then subjected to gel filtration on Sephadex G-50 and ultracentrifugation, where it appeared as a single fraction.
• The researchers then calculated a sedimentation constant of 3.12, which indicates the rate at which a particle falls in a medium, providing insights about its size and shape.
• They also undertook an end-group analysis, which indicated the presence of phenylalanine at both amino and carboxy terminals of the protein.

Amino Acid Analysis and Separation of Components

• The scientists also performed an amino acid analysis of the growth hormone.
• They utilized polyacrylamide column electrophoresis to separate four components of the equine growth hormone.
• Interestingly, they found growth hormone activity in hypophysectomized rats in all four separated components. Hypophysectomized rats are those in which the pituitary gland is surgically removed, causing a lack of growth hormone in their body.

Hormonal Activity and Immunological Tests

• However, the equine growth hormone, even though it was active in the rats, it did not increase plasma free fatty acids in human subjects or show any effect in a human balance study. Tihs suggests that horses may respond differently to this hormone than humans.
• The equine growth hormone also did not react immunologically with antibodies to human growth hormone, whole and pepsin-digested bovine growth hormone, or bovine albumin.
• Despite these inactivities, the hormone showed significant prolactin activity. Prolactin is another hormone that stimulates milk production.
• On the other hand, the hormone did not show any adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), or gonadotropic activity at the dose levels of the assay. These hormones would influence the adrenal glands, the thyroid, and the gonads, respectively.

Conclusions

• This research highlights the unique behaviour of equine growth hormones and underlines the importance of separate study for each species’ hormones.