Prostaglandin F and E synthesis by specific tissue components of the brook trout (Salvelinus fontinalis) ovary

Abstract

The synthesis of prostaglandins (PGs) by several tissue components of brook trout (Salvelinus fontinalis) ovaries was investigated using radiolabeled precursor incorporation and radioimmunoassays for PGE and PGF. PGE2 and PGF2α were synthesized from 14C arachidonic acid (AA) by the follicle walls of mature oocytes. Synthesis was significantly greater in follicles taken postovulation as compared to those sampled prior to germinal vesicle breakdown. However, the most extensive synthesis of PGs occurred with tissue outside of the mature follicles (i.e., extrafollicular[EF]). When incubated with AA, the predominant primary PG produced by this tissue was PGE2. EF tissue could be separated microscopically into two major fractions—immature follicles and stromal tissue. When these tissue fractions were incubated separately with AA the stromal fraction retained the ability to produce PGE2, while the immature follicles increased synthesis of PGF2α. 14C‐Eicosatrienoic acid was converted to PGE1 and PGF1α by EF tissue but in significantly reduced quantities relative to AA. Fatty acid analysis indicated that there were significant quantities of arachidonic, eicosapentaenoic, and docosahexaenoic acids in both follicles and EF tissue, but there was not a significant difference between the two tissues in the absolute amount of arachidonate/mg tissue. In experiments using radioimmunoassays (RIAs), the highest quantities of PGE were measured in incubates containing EF tissue. This supported the results obtained through arachidonic acid incorporation and suggested that this tissue is the primary source of PGE in the brook trout ovary. In contrast, the mature follicules that were undergoing ovulation in vitro produced significant quantities of PGF, whereas the EF tissue production of PGF, measured by RIA, was very low. The results clearly indicate that there are several potential sites for PG synthesis within the trout ovary that differ in their capacity to produce E and F prostaglandins.

Cellular Mechanisms for Orthovanadate-, Phorbol Ester-, and Calcium Ionophore- Stimulated Prostaglandin Production in Brook Trout (Salvelinus Fontinalis) Follicles1

“…To conduct this investigation, ovaries were initially cut into pieces and the follicles were dissected from the extrafollicular tissue under a dissecting microscope s previously described [28]. In the experiments on follicular PG production, groups of 10 follicles were held in 25-ml Erlenmeyer flasks containing 3 ml medium, with or without test agents.…”

Mature males of Arctic charr,Salvelinus alpinus, release F-type prostaglandins to attract conspecific mature females and stimulate their spawning behaviour

“…However, PGs have been identified in the testes of a few species and in semen from chum salmon . As in several other fish species, PGs are involved in ovulation in salmonids (Cetta & Goetz 1982, Stacey & Goetz 1982, Goetz et al . 1989 .…”

Angiotensins stimulate in vitro ovulation and contraction of brook trout (Salvelinus fontinalis) follicles

“…Fish were killed after being anesthetized with 2-phenoxyethanol, and the ovary was removed and held in ice-cooled Cortland medium (Wolf and Quimby 1969) containing 20 mM HEPES, adjusted to pH 7.8 with 1 N NaOH. Intact follicles were dissected from extrafollicular tissue under a dissecting microscope as previously described (Goetz et al 1989). Groups of 10 intact or punctured (see below) follicles were held in 25 ml Erlenmeyer flasks containing 3 ml medium, with or without the test agents, and incubated at 12°C with intermittent agitation for varying lengths of time depending on the experiment.…”

“…The contractility of punctured follicles was expressed as a percentage of the weight of intact follicle controls. The effect of the PG synthesis inhibitor, indomethacin, on the angiotensin-stimulated decrease in weight was studied by coincubating follicles with indomethacin at a concentration (10 gg/ml) which has been shown to block PG production in brook trout follicles (Goetz et al 1989). Within the experiments on ovulation and contraction, all incubations were conducted on follicles taken from the same individuals.…”