Publication Abstract

Prolonged-release gonadotrophin-releasing hormone analogue implants enhance oocyte final maturation and ovulation, and increase plasma concentrations of sulphated C21 steroids in North Sea plaice.

Prolonged-release gonadotrophin-releasing hormone analogue implants enhance oocyte final maturation and ovulation, and increase plasma concentrations of sulphated C21 steroids in North Sea plaice.

A.P. Scott, P.R. Witthames, E.L.M. Vermeirssen and J. Carolsfeld

Reproductively mature female plaice were implanted with 50 µg of Gonadotrophin Releasing Hormone analogue (GnRHa), suspended in either coconut oil or methacrylate resin. The weight ofthe fish increased significantly (due to hydration of the oocytes) and reached a peak between 10 and 14 days. The fish produced several batches of eggs, which were consistently bigger than those produced by control fish. Plasma concentrations of free 17β-oestradiol and glucuronidated testosterone rose briefly (4 days) in response to the GnRHa, but then fell continuously until the end of the experiment (20 days). Plasma concentrations of 5β-pregnane-3α,17,20β-triol(which is a metabolite of 17,20β-dihydroxy-4- pregnen-3-one, the putative oocyte 'maturation-inducing steroid' in plaice) increased significantly at 4 days and reached a peak between 12 and 16 days. Concentrations were still very significantly higherthan starting levels on day 20. Plasma concentrations of 3α,17,21-trihydroxy-5 (3-pregnan-20-one showed a slight increase on day 4 but did not change thereafter. There were no differences between the two methods of administration of GnRHa.

Reference:

A.P. Scott, P.R. Witthames, E.L.M. Vermeirssen and J. Carolsfeld. 1999. Prolonged-release gonadotrophin-releasing hormone analogue implants enhance oocyte final maturation and ovulation, and increase plasma concentrations of sulphated C21 steroids in North Sea plaice. Journal of Fish Biology 55, 316-328

A.P. Scott*, P.R. Witthames*, E.L.M. Vermeirssen* and J. Carolsfeld

Journal of Fish Biology 55, 316-328