Steroid hormones have a wide variety of biological effects and target numerous tissues in both mammals and fishes. During sexual maturation, levels of sex steroids are elevated in trout and salmon, and androgens (testosterone and 11-ketostesterone) selectively promote growth of the heart in male rainbow trout. The investigators recently demonstrated that sex steroids rapidly (10-15 min) increase contractile strength of the rainbow trout heart, in a sex-dependent manner. However, the mechanisms responsible for this effect have not been defined. Contraction of the heart is a complex process, involving many cellular systems, and this process relates directly to fish health and swimming performance. Specific objectives for this interdisciplinary project are to: 1) characterize sex-specific steroid binding to hormone receptors in cardiac cells; 2) identify whether sex steroids selectively promote the metabolism of carbohydrate and energy production to support contractile function; 3) characterize the effects of steroids on calcium storage and release within cardiac muscle cells; and 4) measure heart function and swimming abilities of fish receiving sex steroids at levels present during spawning periods. Trout and salmon are extremely important in the Pacific Northwest, in terms of aquatic ecology, Native American culture, and economic interests. Thus, this project will be of interest to various scientists, regional Native American tribes, and the fish farming industry. The project is also designed to provide students, including those from underrepresented groups, the opportunity to participate in research activities, enhancing their own scientific education and experience. Ultimately, the results may improve environmental management of wild trout and promote a better understanding of vertebrate cardiac function.
