TY - JOUR
T1 - Maternal serum and yolk hormone concentrations in the placental viviparous bonnethead shark, Sphyrna tiburo
AU - Manire, Charles A.
AU - Rasmussen, L. E.L.
AU - Gelsleichter, James
AU - Hess, David L.
N1 - Funding Information:
The authors thank John Tyminski, Kristine Lee, Lisa Holmquist, John Carlson, Linda Lombardi-Carlson, John Brusher, Maria Wise, and Dana Bethea, and many college interns, for their help with collection of samples. They also thank Kelly Bonner, Emily Dail, and Robert McCracken for their help in the yolk extraction procedure. Although the research described in this article has been funded in part by the United States Environmental Protection Agency through Grant # R826128-01-0 to C. Manire, it has not been subjected to the Agency’s required peer and policy review and therefore does not necessarily reflect the views of the Agency and no official endorsement should be inferred.
PY - 2004/4
Y1 - 2004/4
N2 - Among vertebrates, maternal transfer of hormones to offspring has been studied extensively in mammals (placental transfer) and more recently in oviparous birds and reptiles (yolk transfer). The placental viviparous bonnethead shark, Sphyrna tiburo, allows the investigation of both yolk and placental hormone transfers in a single organism. In this species, yolk provides nutrition for the first half of embryonic development and placental transfer provides the second half. As sex determination is complete prior to development of placental connections, it was postulated that yolk hormones would have a prominent role in embryonic regulation. The goal of the current study was to determine serum and yolk hormone concentrations during five reproductive stages, from pre-ovulatory through pre-implantation (pre-placental) stages. Radioimmunoassay was used to determine 17β-estradiol, progesterone, and testosterone concentrations in both serum and yolk. When yolk and serum concentrations were compared, the yolk had significantly higher concentrations of both estradiol and progesterone during post-ovulation and early pregnancy. Yolk concentrations of testosterone were significantly less than serum at pre-ovulation, but there were no differences after that stage. When yolk concentrations were compared between stages, significantly higher concentrations of estradiol were present in ovulatory, post-ovulatory, and pre-implantation stages, while progesterone was significantly higher in post-ovulatory, early pregnancy, and pre-implantation stages and testosterone was higher in pre-ovulation. Most of these results are consistent with the published findings in birds and reptiles. Further, in the bonnethead shark, they suggest that yolk transfer of hormones is adequate for sexual differentiation in embryonic development and that estradiol probably has a significant developmental role.
AB - Among vertebrates, maternal transfer of hormones to offspring has been studied extensively in mammals (placental transfer) and more recently in oviparous birds and reptiles (yolk transfer). The placental viviparous bonnethead shark, Sphyrna tiburo, allows the investigation of both yolk and placental hormone transfers in a single organism. In this species, yolk provides nutrition for the first half of embryonic development and placental transfer provides the second half. As sex determination is complete prior to development of placental connections, it was postulated that yolk hormones would have a prominent role in embryonic regulation. The goal of the current study was to determine serum and yolk hormone concentrations during five reproductive stages, from pre-ovulatory through pre-implantation (pre-placental) stages. Radioimmunoassay was used to determine 17β-estradiol, progesterone, and testosterone concentrations in both serum and yolk. When yolk and serum concentrations were compared, the yolk had significantly higher concentrations of both estradiol and progesterone during post-ovulation and early pregnancy. Yolk concentrations of testosterone were significantly less than serum at pre-ovulation, but there were no differences after that stage. When yolk concentrations were compared between stages, significantly higher concentrations of estradiol were present in ovulatory, post-ovulatory, and pre-implantation stages, while progesterone was significantly higher in post-ovulatory, early pregnancy, and pre-implantation stages and testosterone was higher in pre-ovulation. Most of these results are consistent with the published findings in birds and reptiles. Further, in the bonnethead shark, they suggest that yolk transfer of hormones is adequate for sexual differentiation in embryonic development and that estradiol probably has a significant developmental role.
KW - Bonnethead shark
KW - Estradiol
KW - Hormone
KW - Sphyrna tiburo
KW - Testosterone
KW - Yolk
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U2 - 10.1016/j.ygcen.2003.12.018
DO - 10.1016/j.ygcen.2003.12.018
M3 - Article
C2 - 15028528
AN - SCOPUS:1542404523
SN - 0016-6480
VL - 136
SP - 241
EP - 247
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
IS - 2
ER -