C - Michigan Technological University

2008. Samples were collected as described in section 2.2.1. Information about the bearsused for each serum assay is shown in Table 4.1. Due to limitations of serum samplesizes, not all bears were used for all assays. The choice of bear used for each assaydepended upon sample availability at the time the assays were run. The full-length andc-terminal PTH assays were sandwich ELISAs from Immutopics International (SanClemente, CA). Relative optical densities were reported. Serum melatonin andtestosterone were quantified by RIA by Laurence Demmers at Pennsylvania StateUniversity. All statistical analyses were performed using JMP 7 software. Data in tablesare presented as the LSM + SE. Graphs are represented with a point for each serumsample, and a smoothed average curve generated with JMP software by a cubic spline.All available samples from all bears were grouped by season (i.e. prehibernation,hibernation, and post-hibernation) and analyzed with a single-factor ANOVA, blocking bybear, with a Tukey’s post-hoc.4.3 ResultsSerum concentrations of hormones are reported in Table 4.2. Serum levels oftotal PTH were not affected by season (Figure 4.1). However, levels of the c-terminalfragment of PTH were significantly lower during post-hibernation compared toprehibernation and hibernation seasons (p=0.0164), though the profiles of the two bearswere different (Figure 4.2). Testosterone decreased from 54.7 ng/dL in prehibernation to17.4 ng/dL in post-hibernation (p=0.0361) (Figure 4.3). Melatonin was belowquantifiable levels in all serum samples.4.4 DiscussionThe goal of this study was to determine whether hormone concentrations in theserum of hibernating bears favored anti-apoptotic conditions for osteoblasts; therefore,concentrations of three hormones which regulate osteoblast apoptosis were quantified inthe serum of hibernating and active American black bears. Melatonin has anti-apoptoticeffects on osteoblasts [58], and administration of melatonin to ovariectomized ratsdecreases apoptosis and abates bone loss [253]. However, this study found that65