TY - JOUR
T1 - Effects of larval exposure to estradiol on spermatogenesis and in vitro gonadal steroid secretion in African clawed frogs, Xenopus laevis
AU - Hu, Fang
AU - Smith, Ernest E.
AU - Carr, James A.
N1 - Funding Information:
We acknowledge Dr. Reynaldo Patiño and Dr. Chris Theodorakis for providing space in their respective laboratories. We thank Dr. Reynaldo Patiño for helping in identifying type of germ cells. This research was performed in partial fulfillment of the Ph.D. degree by F.H. and was supported in part by funding from a Texas Tech University interdisciplinary seed grant.
PY - 2008/1/1
Y1 - 2008/1/1
N2 - Estrogen or eco-estrogenic chemicals can disrupt normal gonadal sex differentiation, causing intersex formation and feminization in amphibians. The cellular basis for estrogen-induced sex reversal is not well understood. In the present study, we investigated the concentration- and stage-dependent effects of estradiol (E2) exposure during the larval period on histological characteristics of gonadal sex differentiation and gonadal sex steroid secretion in vitro in the African clawed frog, Xenopus laevis. Embryos were exposed to E2 (1, 10, or 100 μg/L) or vehicle control through metamorphosis and then allowed to develop in untreated medium for 2-mo post-metamorphosis. To investigate gonadal sex differentiation and development during and after exposure, gonadal samples were collected at different developmental stages. Gonadal sex differentiation did not occur before NF stage 52 in any group. At NF stage 54-55 primordial germ cells (PGCs) were observed in both cortical and medullary regions of developing tadpoles gonads in the control, 1 and 10 μg/L E2 treatments, but were observed only in the cortical region of tadpoles exposed to 100 μg/L E2. E2 increased the percent of spermatocytes, spermatids, and spermatozoa compared to controls. Larval E2 exposure did not alter hCG-induced gonadal testosterone secretion in vitro but significantly increased E2 secretion from ovaries of juvenile frogs. Our results indicate that E2 exposure during larval development appears to prevent PGC migration to the medulla of developing gonads in a concentration-dependent manner. The degree of PGC migration to the medulla may be related to the degree of E2-induced intersex formation and feminization in X. laevis. E2 exposure during the larval period accelerates spermatogenesis and can increase ovarian E2 secretion in juvenile frogs.
AB - Estrogen or eco-estrogenic chemicals can disrupt normal gonadal sex differentiation, causing intersex formation and feminization in amphibians. The cellular basis for estrogen-induced sex reversal is not well understood. In the present study, we investigated the concentration- and stage-dependent effects of estradiol (E2) exposure during the larval period on histological characteristics of gonadal sex differentiation and gonadal sex steroid secretion in vitro in the African clawed frog, Xenopus laevis. Embryos were exposed to E2 (1, 10, or 100 μg/L) or vehicle control through metamorphosis and then allowed to develop in untreated medium for 2-mo post-metamorphosis. To investigate gonadal sex differentiation and development during and after exposure, gonadal samples were collected at different developmental stages. Gonadal sex differentiation did not occur before NF stage 52 in any group. At NF stage 54-55 primordial germ cells (PGCs) were observed in both cortical and medullary regions of developing tadpoles gonads in the control, 1 and 10 μg/L E2 treatments, but were observed only in the cortical region of tadpoles exposed to 100 μg/L E2. E2 increased the percent of spermatocytes, spermatids, and spermatozoa compared to controls. Larval E2 exposure did not alter hCG-induced gonadal testosterone secretion in vitro but significantly increased E2 secretion from ovaries of juvenile frogs. Our results indicate that E2 exposure during larval development appears to prevent PGC migration to the medulla of developing gonads in a concentration-dependent manner. The degree of PGC migration to the medulla may be related to the degree of E2-induced intersex formation and feminization in X. laevis. E2 exposure during the larval period accelerates spermatogenesis and can increase ovarian E2 secretion in juvenile frogs.
KW - Amphibians
KW - Endocrine disruption
KW - Gonadal sex differentiation
KW - Intersex
KW - Sex differentiation
KW - Sex steroids
UR - http://www.scopus.com/inward/record.url?scp=36248931060&partnerID=8YFLogxK
U2 - 10.1016/j.ygcen.2007.04.015
DO - 10.1016/j.ygcen.2007.04.015
M3 - Article
C2 - 17544424
AN - SCOPUS:36248931060
VL - 155
SP - 190
EP - 200
JO - General and Comparative Endocrinology
JF - General and Comparative Endocrinology
SN - 0016-6480
IS - 1
ER -