Unique metabolites of eicosapentaenoic acid interfere with corpus luteum function in the ewe.

Experiments were conducted to determine the in vivo and in vitro effects of metabolites of eicosapentaenoic acid on ovine luteal function. Injection of 750 micrograms methyl eicosapentaenoic acid (EPA) or methyl 12(R),13(S)-dihydroxyeicosapentaenoic acid (12,13-diHEPE) into the ovarian artery of ewes on day 10 of the estrous cycle caused a reduction in serum concentrations of progesterone by 48 h posttreatment compared with levels of this steroid in arachidic acid-treated controls (p < 0.005). Although mean serum concentrations of progesterone in methyl EPA-treated ewes during the remainder of the cycle did not differ from those in control ewes, levels in methyl 12,13-diHEPE-treated ewes remained significantly suppressed. Duration of the estrous cycle did not differ among treatment groups (p > 0.05), but more of the methyl 12,13-diHEPE-treated animals (3/5) had exhibited estrus within 3 days after injection than methyl EPA-treated (1/5) or control ewes (0/5). Slices of corpus luteum removed from ewes on day 10 of the estrous cycle were incubated with arachidic acid (controls), 12,13-diHEPE or docosatetraenoic acid (DTA). Regardless of fatty acid treatment, all tissues retained the ability to produce basal levels of progesterone during subsequent incubation. Luteal slices previously exposed to arachidic acid or DTA exhibited an increase in progesterone production in response to subsequent treatment with LH (p < 0.05). In contrast, luteal slices incubated with 12,13-diHEPE did not respond to LH with a significant increase in production of this steroid above that observed in controls. All tissues displayed a marked increase in progesterone synthesis upon treatment with 8-Br-cAMP relative to incubation of tissue alone (p < 0.001). Subcellular distribution of [14C]-12,13-diHEPE in luteal cells after incubation revealed that the majority of the fatty acid was associated with the plasma membrane. These data suggest that metabolites of eicosapentaenoic acid with hydroxyl groups on adjacent carbon atoms interfere with luteal function in the ewe, perhaps in part by altering luteal response to LH.     

The acute phase response of rainbow trout (Oncorhynchus mykiss) plasma proteins to viral, bacterial and fungal inflammatory agents

The innate arm of the immune system responds to inflammatory stimuli by the activation of phagocytes, and by altered levels of several plasma proteins. These changes in plasma proteins comprise a major component of the acute phase response, which is thought to be an adaptive response that contributes to regaining homeostasis after tissue injury or infection. In this study, rainbow trout (Oncorhynchus mykiss) were injected with a variety of potential inflammatory agents, and changes in the concentrations of plasma proteins were sought in polyacrylamide gels in which plasma proteins had been electrophoresed. Bacteria, viruses and yeast all induced changes in plasma protein profiles. Increases were first evident 2 days after injections, and most were evident within 1 week. The greatest number of changes occurred after injection with a Vibrio bacterin emulsified in Freund's incomplete adjuvant. While some proteins increased and others decreased following several treatments, other proteins changed only in response to injections of viruses or viral proteins, and others changed in response to bacterial components. Some proteins that increased after yeast injection decreased after injection of viral components. The partial amino acid sequence of one increased protein identified it as haptoglobin.     

Eicosanoids from the Rhodophyta: new metabolism in the algae

Red marine algae are shown in this work to be a rich source of eicosanoid-type natural products. This is the first isolation of several of these mammalian arachidonic acid metabolites from any marine or terrestrial plant source (12-HETE, 12-HEPE, 6(E)-LTB4, hepoxilin B3). A few of these represent truly novel substances never previously isolated from nature [12(R), 13(S)-diHETE]. Inherent in these seaweed natural product structures is evidence for a highly evolved lipoxygenase-type metabolism that matches or exceeds the complexity of comparable metabolic routes in mammalian systems. As these compounds are produced by algae in relatively large quantities (0.1–5.0% of crude lipid extracts), these plants could be important commercial resources for these expensive and rare biochemicals. Further, we suggest that this metabolism is important to physiological processes in red algae that are completely unknown at present. For example, it is possible that they act in an exocrine sense to coordinate reproductive events, a hypothesis under current investigation through culture studies.This paper was presented at the mini-symposium Bioactive Compounds from Algae, Y. Shimizu, Convener.     

Pilot scale culture of the marine cyanobacterium Lyngbya majuscula for its pharmaceutically-useful natural metabolite curacin A

A Caribbean collection of Lyngbya majuscula which produces the promising antimitotic agent, curacin A, was recollected in 1993 from Curaçao and adapted to laboratory culture. A variety of culture vessel configurations and conditions were examined for their effect on growth and production of curacin A. Using these partially optimized conditions, 29 strains of curacin A producing L. majuscula were evaluated for their production levels of curacin A employing an internal standard GC-MS analytical method. Five strains were more carefully characterized for their growth and curacin A production, and led to our selection of one reliable strain, ’19L‘, for further studies. Growth and curacin A production curves were established for this strain over a 30 day growth period. This directed a scale-up culture of 640 liters of L. majuscula strain 19L in four batches of 160 L each. All four batches grew well and produced significant quantities of curacin A. In tota1, 215.5 g wet weight of L. majuscula tissue were produced which gave an isolated yield of 132.5 mg of curacin A.