Changes in Plasma Gonadotropin II and Sex Steroid Hormones, and Sperm Production of Striped Bass after Treatment with Controlled-Release Gonadotropin-Releasing Hormone Agonist-Delivery Systems1

Abstract

Spermiating striped bass, a perciform fish, were treated with two controlled-release gonadotropin-releasing hormone agonist (GnRHa)-delivery systems, and the resulting changes in plasma gonadotropin II (GTH II), testosterone (T), 11-ketotestosterone (11-KT), 17,20beta-dihydroxy-4-pregnen-3-one (17,20beta-P), and 17,20beta,21-trihydroxy-4-pregnen-3-one (17,20beta,21-P) were correlated with changes in milt production and sperm density. GnRHa-delivery systems induced a sustained elevation of plasma GnRHa and GTH II for 14 days. Plasma T levels were unchanged after GnRHa treatment, while 11-KT levels increased significantly. Plasma 17,20beta-P also increased after GnRHa treatment and remained elevated compared to levels in controls, while plasma 17,20beta,21-P levels were unaffected. Both GnRHa-delivery systems induced many-fold increases in total expressible milt, lasting throughout the 14 days of the study. Sperm density decreased 2 days after GnRHa treatment, with a subsequent increase by Day 7. This study demonstrates that GnRHa-delivery systems induce a sustained elevation of plasma GTH II levels in striped bass, resulting in a long-term enhancement of milt production. The endocrine changes observed suggest that 11-KT and 17,20beta-P, but not 17,20beta,21 -P, are mediating the effects of GTH II on spermiation.

A quantitative HPLC–MS method for the simultaneous determination of testosterone, 11-ketotestosterone and 11-β hydroxyandrostenedione in fish serum

“…The obtained values where 92 ± 5 (n = 6), 102 ± 13 (n = 6), and 92 ± 7% (n = 6) for 11-KT, 11␤-OH 4 and T, respectively. These results were comparable to those presented for similar compounds using the same extraction method [36,37].…”

“…Precision for the analysis of T, 11-KT, and 11␤-OH 4 in serum samples of adult goldfish prepared and analyzed in three different days (three replicates per day their reproductive life (see for Goldfish [34], Japanese Huchen (Hucho perryi) [35], Striped Bass (Morone saxatilis) [36]). …”

Individual contributions to pooled-milt fertilizations of silver catfish Rhamdia quelen

“…The milt from each male was evaluated separately. To estimate the sperm concentration, 10 µl of milt was diluted in 2 ml of 5% formalin (in buffered saline), and the number of spermatozoa was counted in a Neubauer chamber under a microscope (400x), according to Mylonas et al (1997). Spermatocrit values were determined for sperm collected in capillary tubes and centrifuged at 3000 rpm during 5 min.…”

Polychlorinated biphenyls, mercury, and potential endocrine disruption in fish from the Hudson River, New York, USA

“…Modulation of endocrine biomarkers in blood plasma has been correlated with environmental contaminants and potential adverse effects on reproductive capacity (USEPA, 1997;Kime, 1998;Schmitt and Dethloff, 2000). The sex-steroid hormone, 17b-estradiol (E2) regulates oogenesis in female fish and 11-ketotestosterone (11KT) controls spermatogenesis in males of many fish species (Mylonas et al, 1997;Cavaco et al, 1999;Todo et al, 1999), even though testosterone is the most important androgen in female of most fish species (Lokman et al, 2002) and some fish species have negative 11KT males (Borg, 1994). The concentrations of both hormones fluctuate widely throughout the year; E2 normally occurs at higher levels in females than in males, whereas 11KT normally occurs at higher levels in males than in females of the same species (Kime, 1998;Schmitt and Dethloff, 2000).…”