Ikonomopoulou M P, Ibrahim K, Bradley A J
School of Biomedical Sciences, The University of Queensland, Brisbane, QLD 4072, Australia.
J Comp Physiol B. 2008 Sep;178(7):837-43. doi: 10.1007/s00360-008-0271-y. Epub 2008 May 17.
Sex steroid binding proteins were identified in hatchling female and male Chelonia mydas by dialysis and steady-state gel electrophoresis when examined at 4 degrees C. A testosterone binding protein with high binding affinity (K (a) = 0.98 +/- 0.5 x 10(8) M(-1)) and low to moderate binding capacity (B (max) = 7.58 +/- 4.2 x 10(-5) M) was observed in male hatchlings. An oestradiol binding protein with high affinity (K (a) = 0.35 +/- 1.8 x 10(8) M(-1)) and low to moderate binding capacity (B (max) = 0.16 +/- 0.5 x 10(-4) M) was identified in female hatchlings. This study confirmed that sex steroid binding proteins (SSBPs) become inactivate in both sexes at 36 degrees C, the maximum body temperature of sea turtle hatchlings at emergence. The inactivation of SSBPs at this temperature indicates that sex steroid hormones circulate freely in the body of the green turtles and are biologically available in the blood plasma. This observation is consistent with female and male hatchling C. mydas having different physiological (hormonal) and developmental requirements around the time of emergence. Moreover, concurrently conducted competition studies showed that sex steroids including testosterone and oestradiol do compete for binding sites in both male and female C. mydas hatchling plasma. Competition also occurred between testosterone and dihydrotestosterone for binding sites in the male C. mydas plasma. However, competition studies in the plasma of female hatchling C. mydas demonstrate that oestrone does not compete with oestradiol for binding sites.
在4摄氏度下进行检测时，通过透析和稳态凝胶电泳在孵化出的雌性和雄性绿海龟中鉴定出性类固醇结合蛋白。在雄性幼龟中观察到一种具有高结合亲和力（K(a)=0.98±0.5×10⁸ M⁻¹）和低至中等结合能力（B(max)=7.58±4.2×10⁻⁵ M）的睾酮结合蛋白。在雌性幼龟中鉴定出一种具有高亲和力（K(a)=0.35±1.8×10⁸ M⁻¹）和低至中等结合能力（B(max)=0.16±0.5×10⁻⁴ M）的雌二醇结合蛋白。这项研究证实，性类固醇结合蛋白（SSBPs）在36摄氏度时在两性中均失活，36摄氏度是海龟幼龟出壳时的最高体温。在此温度下SSBPs的失活表明性类固醇激素在绿海龟体内自由循环，并且在血浆中具有生物活性。这一观察结果与雄性和雌性绿海龟幼龟在出壳前后具有不同的生理（激素）和发育需求相一致。此外，同时进行的竞争研究表明，包括睾酮和雌二醇在内的性类固醇确实会竞争雄性和雌性绿海龟幼龟血浆中的结合位点。睾酮和双氢睾酮也会竞争雄性绿海龟血浆中的结合位点。然而，对雌性绿海龟幼龟血浆的竞争研究表明，雌酮不会与雌二醇竞争结合位点。
