| Popis: |
Sheep producers are continually faced with the need to increase pounds of retail product sold. One way to increase total retail pounds of lamb available for consumption without increasing sheep numbers or producer costs is through genetic selection for increased size and growth. Another option would be to select sheep with the callipyge mutation or understand what the mutation changes to increase growth. Callipyge is a selective hypertrophic condition exhibited primarily in the hind limbs of affected lambs. The cause of the increased growth at a molecular level has not been thoroughly explored. Other studies have evaluated differences in satellite cells (SC) isolated from high and low growth line animals but none compared normal and callipyge sheep satellite cells using defined media. The objective of the present study was to compare the effect of genotype (normal and callipyge), growth compound (estradiol benzoate, trenbolone acetate, IGF-I, and FGF) and level of growth compound (0, 2.5, 5, 10, 30, and 50 ng/μL) on proliferation of sheep satellite cells. Sheep SC isolated from normal and callipyge sheep were evaluated. Cells were plated and grown in standard growth media for three days and then treated with estradiol benzoate, trenbolone acetate, FGF, and IGF-I in a defined growth media. Proliferation differences between SC types and hormones were evaluated. At intervals of 24 h, SC were fixed, stained, and counted. Data interpretation may be inhibited due to concerns with experimental design and procedures; however, in the present experiment callipyge and normal SC proliferated at similar rates when not exposed to any growth compound. While the difference in number of SC at 24 h and 48 h of growth was significant, there was not a significant interaction between cell genotype and time of growth. A significant interaction between genotype and growth promoting compound was seen. Proliferation of callipyge SC was greater in response to IGF-I than normal SC; callipyge SC proliferated less in response to FGF than did normal SC. Cells deprived of FGF and IGF-I did not exhibit impaired proliferation as expected. Response to IGF-I may explain some differences that are seen in the callipyge phenotype. |
