Endocrine changes associated with overripening of ovulated eggs in goldfish, Carassius aurutus
1995
Formacion, M.J. | Lam, T.J.
Changes in steroid hormone levels in the serum and ovarian fluid were studied during overipening in goldfish. Ovulated eggs retained in the ovarian cavity become overripe at around 12 h after ovulation and completely overripe 24 h after. Blood and ovarian fluid were taken at 0, 3, 6, 12, 18 and 24 h after ovulation. Estradial-117B (E2), testosterone (T), progesterone (P) and 17a, 20-B-dehydroxy-4, pregnen-3-one (17,20B-P) in the serum were extracted directly with a solvent while those in the ovarian fluid were separated by HPLC before radioimmunoassay. Both serum and ovarian fluid P showed a highly significant decline at 18 h with a further decline at 24 h. P levels were higher in the ovarian fluid. Serum 17, 20B-P showed a progressive and more rapid decline, decreasing significantly at 12 h with further decreases at 18 h and 24 h; the level was five-fold lower at 24 h compared to the zero h level. Serum T increased significantly at 3 h which was maintained until 18 h, when it declined to zero h level. No significant changes in E2 were observed in the serum, except for a significant difference between 6 and 24 h. There were no significant changes in E2, T and 17, 20B-P in the ovarian fluid. Of the four steroids measured, only 17, 20B-P and P showed changes which bore some correlation with the time course of overripening. The declines in the mean ratios of 17, 20B-P/E2 in the ovarian fluid also appeared to have good correlations with the time course of overripening. The (post ovulatory follicles POFs) showed degenerative features which likewise corresponded to the decline in P and 17, 20B-P
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