Growth hormones (GH) control the growth, metabolism and deposition of muscle and fat in mammals and poultry as well as growth in fish. With funding from USDA's Cooperative State Research, Education, and Extension Service's (CSREES) National Research Initiative (NRI) program, scientists examined how secretion of growth hormones in individual cells is induced.
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| The presence of somatotropes was confirmed by immunocytochemical staining with anti-GH antibody Credit: Lloyd Anderson |
Deep at the base of the brain, the pea-sized pituitary gland is part of the endocrine system that secretes hormones to regulate bodily functions. Specialized cells, called somatotropes, secrete a growth hormone that controls growth and metabolism in animals.
Somatotropes, however, do not automatically secrete growth hormones. It takes many different GH-releasing hormones to stimulate somatotropes to secrete growth hormones. Being able to regulate the release of growth hormones may have a powerful impact on the quality of animal products and on medical treatments in humans.
Colin Scanes, Lloyd Anderson and colleagues at the Iowa State University examined calcium ion sensitivity to GH-releasing hormones. The scientists determined that one specific GH-releasing hormone, called gonadotropin-releasing hormone (GnRH), expressed calcium ion sensitivity in 40 percent of somatotropes. Interestingly, the GnRH releasing activity decreased in calcium ion-poor mediums.
The calcium ion sensitivity found in specific GH-releasing hormones may reflect how different types of cells communicate. This work expands on what is known of the different types of somatotropes and the preliminary evidence of how these cells function.
Scientists know that GnRH stimulates the release of growth hormones in several important fish species, including tilapia and rainbow trout. The findings from this project may lead to improvements in management and feeding strategies to naturally stimulate the release of growth hormones in agriculturally important animals.