Manire C A, Rasmussen L E, Gross T S
Center for Shark Research, Mote Marine Laboratory, Sarasota, Florida 34236, USA.
J Exp Zool. 1999 Oct 1;284(5):595-603. doi: 10.1002/(sici)1097-010x(19991001)284:5<595::aid-jez15>3.0.co;2-6.
Previous studies in the placental viviparous bonnethead shark, Sphyrna tiburo, have correlated 17 beta-estradiol, progesterone, testosterone, and dihydrotestosterone with reproductive events in both males and females. However, several key reproductive events, including implantation, maintenance of pregnancy, and parturition, did not correlate with these four steroid hormones. Therefore, the present study investigated three steroid hormones, 11-ketotestosterone, 11-ketoandrostenedione, and dihydroprogesterone, which have demonstrably important roles in the reproductive cycles of teleosts. It was hypothesized that one or more of these three hormones would correlate with specific reproductive events in S. tiburo. Concurrently, developmental (growth and/or maturation) analyses of these three steroids plus 17 beta-estradiol, progesterone, testosterone, and dihydrotestosterone were investigated in juvenile bonnethead sharks. Serum dihydroprogesterone concentrations were highest in mature females and 11-ketotestosterone concentrations were highest in mature males. In mature females, 11-ketoandrostenedione levels were elevated from the time of mating, through six months of sperm storage and another four months of gestation. At parturition concentrations became significantly lower and remained lower until mating occurred again in another two to three months. Serum 11-ketotestosterone concentrations were the highest at implantation though not significant. In mature males, significantly elevated serum levels of dihydroprogesterone occurred in April and May, near the start of annual testicular development. During growth in males, testosterone and dihydrotestosterone increased progressively and in females, testosterone increased progressively. At maturity in males, significant increases occurred in testosterone and 11-ketotestosterone concentrations while, in females, dihydroprogesterone, 11-ketotestosterone, 17 beta-estradiol, progesterone, testosterone, and dihydrotestosterone concentrations increased. This study shows that although testosterone may be the primary androgen in the bonnethead shark, other derived androgens may have important functions in growth, maturation, and reproduction. J. Exp. Zool. 284:595-603, 1999.
以往对胎生的窄头双髻鲨（Sphyrna tiburo）的研究表明，17β-雌二醇、孕酮、睾酮和双氢睾酮与雄性和雌性的生殖事件相关。然而，包括着床、维持妊娠和分娩在内的几个关键生殖事件与这四种甾体激素并无关联。因此，本研究调查了三种甾体激素，即11-酮睾酮、11-酮雄烯二酮和双氢孕酮，它们在硬骨鱼的生殖周期中具有显著的重要作用。研究假设这三种激素中的一种或多种与窄头双髻鲨的特定生殖事件相关。同时，对幼年窄头双髻鲨体内这三种甾体激素以及17β-雌二醇、孕酮、睾酮和双氢睾酮进行了发育（生长和/或成熟）分析。成熟雌性血清中双氢孕酮浓度最高，成熟雄性血清中11-酮睾酮浓度最高。在成熟雌性中，从交配时起，经过6个月的精子储存期和另外4个月的妊娠期，11-酮雄烯二酮水平一直升高。分娩时其浓度显著降低，并一直保持较低水平，直到再过两到三个月再次交配时才恢复。血清11-酮睾酮浓度在着床时最高，但不显著。在成熟雄性中，4月和5月，即年度睾丸发育开始时，血清双氢孕酮水平显著升高。在雄性生长过程中，睾酮和双氢睾酮逐渐增加，在雌性中，睾酮逐渐增加。雄性成熟时，睾酮和11-酮睾酮浓度显著增加，而在雌性中，双氢孕酮、11-酮睾酮、17β-雌二醇、孕酮、睾酮和双氢睾酮浓度均增加。本研究表明，尽管睾酮可能是窄头双髻鲨的主要雄激素，但其他衍生雄激素在生长、成熟和繁殖中可能具有重要作用。《实验动物学杂志》284:595 - 603，1999年。
