Prostaglandin biosynthesis in the skin of the plaice Pleuronectes platessa L

Prostaglandins in Marine Organisms: A Review

Prostaglandins (PGs) are lipid mediators belonging to the eicosanoid family. PGs were first discovered in mammals where they are key players in a great variety of physiological and pathological processes, for instance muscle and blood vessel tone regulation, inflammation, signaling, hemostasis, reproduction, and sleep-wake regulation. These molecules have successively been discovered in lower organisms, including marine invertebrates in which they play similar roles to those in mammals, being involved in the control of oogenesis and spermatogenesis, ion transport, and defense. Prostaglandins have also been found in some marine macroalgae of the genera Gracilaria and Laminaria and very recently the PGs pathway has been identified for the first time in some species of marine microalgae. In this review we report on the occurrence of prostaglandins in the marine environment and discuss the anti-inflammatory role of these molecules.

Dietary supplementation with arachidonic acid in tilapia (Oreochromis mossambicus) reveals physiological effects not mediated by prostaglandins

This study aims to clarify the role of the polyunsaturated fatty acid arachidonic acid (ArA, 20:4n-6) in the stress response of Mozambique tilapia (Oreochromis mossambicus). ArA is converted into eicosanoids, including prostaglandins, which can influence the response to stressors. Tilapia, a species able to form ArA from its precursor, was supplemented with ArA for 18 days, after which they were confined for 5 min. Acetylsalicylic acid (ASA, COX-inhibitor) was subsequently administered to distinguish ArA-mediated effects from enhanced prostaglandin E(2) (PGE(2)) synthesis. ArA supplemented fish had higher ArA levels in gills and kidneys, and these levels were further enhanced after ASA treatment. Levels of total monounsaturated and polyunsaturated fatty acids as well as docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and ArA, were altered 24h after confinement, particularly in the kidneys. ArA supplementation had no effect on basal cortisol levels, while ArA + ASA reduced basal cortisol levels. ArA + ASA augmented the cortisol response to confinement. The combination of ArA + ASA also elevated plasma basal prolactin (tPRL)(177) and 3,5,3'-triiodothyronine (T(3)) levels. Neither ArA nor ASA affected the stress-associated increases in plasma glucose and lactate. Na(+), K(+)-ATPase activity in the gills was reduced after ArA supplementation and was even further suppressed by subsequent ASA treatment. In an additional feeding trial, ArA supplementation enhanced the renal Na(+), K(+)-ATPase activity. In vitro, ArA was a potent inhibitor of the Na(+), K(+)-ATPase activity of gill and kidney homogenates. In contrast, PGE(2) had no effect on branchial ATPase, whereas the effect on renal ATPase activity was concentration dependent. Modifying the dietary intake of ArA alters the response of tilapia to an acute stressor and influences osmoregulatory processes and it is unlikely that these effects are due to an enhanced production of prostaglandins.

Prostaglandin synthesis in goldfish heart, Carassius auratus

Potential precursors for prostaglandin (PG) synthesis were measured in goldfish heart and skeletal muscle by gas chromatography. Heart tissue contained docosahexaenoic, arachidonic, eicosapentaenoic, and eicosatrienoic acids in concentrations of 3223 +/- 128, 1216 +/- 7.8, 260 +/- 72.8, and 250 +/- 14 ng/mg wet wt, respectively. 14C-Labeled substrates were examined for their ability to be converted to prostaglandins. Eicosatrienoic and docosahexaenoic acid were not synthesized into prostaglandins, with 66 and 72% of the substrate remaining as free fatty acids, respectively. In contrast, both arachidonic and eicosapentaenoic acids were converted predominantly to PGFs and PGIs. The conversion was time dependent and complete by 30 min. The conversion patterns with eicosapentaenoic acid and arachidonic acid were essentially the same. The data suggest that goldfish cyclooxygenase can utilize two of the four potential substrates for prostaglandin synthesis. As fatty acid levels in fish vary with environmental temperature, substrate availability rather than cyclooxygenase preference may dictate the types of prostaglandins which are produced.