Influence of gonadotropic hormone-releasing hormone analog (GnRH-A) on plasma sex steroid profiles and milt production in male winter flounder, Pseudopleuronectes americanus (Walbaum)

Abstract

The effects of gonadotropic hormone-releasing hormone analog (GnRH-A) treatment on the onset and duration of increases in plasma sex steroids and milt production (milt volume and number of spermatozoa) were investigated in prespawning male winter flounder. After treatment of maturing males during the winter with a single injection of either 20 or 200 μg/kg [D-Ala(6), Pro(9)-NHEt]LHRH (GnRH-A), plasma levels of testosterone and 11-ketotestosterone were increased within 12h and the steroid hormone levels remained elevated for long periods lasting several days. The androgenic steroid response of males was delayed after the administration of a lower dose of GnRH-A (2 μg/kg). Although a single GnRH-A injection in December or January advanced the onset of spermiation in some males, only small amounts (<50 μl) of milt could be collected. By March, all males were in spermiating condition following GnRH-A treatment; however, significant increases in sperm production, particularly increases in milt volume, occurred in fish twice treated with GnRH-A.

Effects of gonadotropin-releasing hormone analog on milt production enhancement in starry flounder Platichthys stellatus

“…In the present study, GnRHa treatment increased milt volume and sperm production in male starry flounder. The increase in milt volume by GnRHa was consistent with all previous studies on fish species 3,4,7,15–20 . However, in previous studies, it was not clear whether the increased milt volume resulted mainly from the increase of actual sperm production or of milt fluidity (measured by spermatocrit or sperm concentration).…”

“…However, in previous studies, it was not clear whether the increased milt volume resulted mainly from the increase of actual sperm production or of milt fluidity (measured by spermatocrit or sperm concentration). In some studies, the increase of milt volume by GnRHa was not accompanied by the increase of milt fluidity, but there was increased sperm production 3,16,18,19 …”

Seasonal changes in the biochemistry of seminal plasma and sperm motility in the ocean pout,Macrozoarces americanus

“…To date, most studies of the fish spermiation response have focused on the sperm of salmonid, cyprinid and a few marine species which are all external egg fertilizers (Scott and Baynes 1980;Morisawa et al 1983;Stoss 1983;Kruger et al 1984;Billard 1986;Billard et al 1993;Suquet et al 1993;Harmin and Crim 1993;Lahnsteiner et al 1994;Billard et al 1995). In contrast, studies of sperm biochemistry and physiology in internally fertilizing teleosts have been limited to some observations of guppy (Billard and Cosson 1990) and sculpin sperm (Koya et al 1993).…”

Puberty and recrudescence in cultured male yellowtail flounder: plasma androgens and spermatogenesis

“…Blood collections on processing dates were kept on ice until centrifugation (10 min, 8325 g , 4° C). The isolated plasma was stored at −20 or −70° C until analysis for the presence of 11‐KT and T. The protocol used to measure 11‐KT was adapted from that of Harmin & Crim (1993) which involved double ether extractions of plasma samples. Departures from the Harmin & Crim (1993) protocol included the use of c .…”

“…The isolated plasma was stored at À20 or À70 C until analysis for the presence of 11-KT and T. The protocol used to measure 11-KT was adapted from that of Harmin & Crim (1993) which involved double ether extractions of plasma samples. Departures from the Harmin & Crim (1993) protocol included the use of c. 13 000 CPM (counts per minute) of 3 H-11-KT tracer per tube, as well as dilution factors for 11-KT antibody of 1 : 30 000 or 1 : 50 000. Testosterone was measured using a no-extraction, solid phase 125 I radioimmunoassay (Coat-A-Count 1 , Diagnostic Products Corporation, Los Angeles, CA, U.S.A.).…”