Determination of prostaglandin precursors in frog tissue using selected-ion monitoring in gas chromatographic-mass spectrometric analysis

Enhanced detection of olefins using ambient ionization mass spectrometry: Ag+ adducts of biologically relevant alkenes

Spray solvent doped with silver ions increases the ease of olefin detection by desorption electrospray ionization (DESI). Characteristic silver adducts were generated in up to 50 times greater abundance when compared to conventional DESI spray solvents for the biologically significant olefin, arachidonic acid, in the positive ion mode. In the analysis of 26 lipids, silver adduct formation was highly favorable for fatty acids, fatty acid esters and prostaglandins but not applicable to some other classes (e.g., polar lipids such as ceramide and its derivative cerebroside sulfate). An investigation exploring competitive Ag(+) cationization with a mixture of components demonstrated that polyunsaturated compounds form Ag(+) adducts most readily. Silver cationization allowed the distinction between three sets of isomers in the course of multiple-stage collision-induced dissociation, so providing insight into the location of the olefin bonds. A silver ion-doped solvent was used in DESI imaging of normal and tumor canine bladder tissue sections. The Ag(+) fatty acid adducts permitted post facto differentiation between the normal and tumor regions. In addition, silver adduct formation in the course of DESI imaging of tissue sections revealed the presence of triacylglycerides, a class of compounds not previously identified through DESI imaging. A simple silver nitrate spray solvent has the potential to further improve DESI analysis of unsaturated biomolecules and other molecules containing π-bonds through selective silver cationization.

Leukotriene C4-stimulated contractions in bullfrog lung are affected by cold acclimation and calcium antagonists

Leukotriene C4 (LTC4) contracts isolated bullfrog lung. This study examined effects of cold-acclimation and the involvement of extracellular and intracellular Ca++ on the contractile response to LTC4. The response to LTC4 was greater in lungs from warm-acclimated (22 degrees C) frogs compared with cold-acclimated (5 degrees C) frogs at incubation temperatures of both 22 degrees C and 5 degrees C. LTC4, LTC5, and N-methyl LTC4 were equally effective in stimulating lung contraction at concentrations from 1-100 nM. Nicardipine (3 microM) partially antagonized the response to LTC4, but verapamil, nifedipine, or nitrendipine at the same concentration was ineffective. Ethylene glycol tetraacetic acid (EGTA, 0.3 mM) prevented the response to 30 nM LTC4, but the response was restored when the lung was retested in EGTA-free medium containing Ca++, suggesting that extracellular Ca++ was involved in the response. Caffeine (10 mM) or thapsigargin (1 mM) inhibited the responses to LTC4, suggesting a role for intracellular Ca++ in the contraction.

Epinephrine stimulates prostaglandin synthesis by bullfrog lung from warm-acclimated, but not cold-acclimated, animals

Exogenous prostaglandins (PGs) have been shown to have differing effects on frog lung contractility. In this study, prostaglandin synthesis was measured in lung tissues from warm-acclimated (WA, 22 degrees C) and cold-acclimated (CA, 5 degrees C) American bullfrogs, Rana catesbeiana, incubated for 30 min at 5 degrees or 22 degrees C. Media were assayed by radioimmunoassay for PGE2, PGF2 alpha, 6-keto PGF 1 alpha (the metabolite of PGI2), and thromboxane (TX)B2 (the metabolite of TXA2). PGE2 was produced in greatest quantity by tissues from WA and CA animals, at both incubation temperatures. Epinephrine stimulated PGE2, PGF2 alpha, and TXB2 synthesis at 22 degrees C but only stimulated PGE2 production at 5 degrees C. In tissues from CA frogs, epinephrine did not stimulate prostaglandin synthesis at either incubation temperature. Ibuprofen (10(-5) M) inhibited basal and epinephrine-stimulated prostaglandin synthesis in tissues from WA frogs incubated at 22 degrees C. The beta receptor antagonist propranolol (10(-6) M) blocked the epinephrine-stimulated synthesis of PGE2, PGF2 alpha and TXB2, suggesting epinephrine stimulates prostaglandin synthesis through beta receptor activation. The absence of stimulation by epinephrine in lung from CA animals, but not in 5 degrees C incubations of tissues from WA animals, suggests that a modification of beta receptors occurs during prolonged cold exposure.

Quantitative determination of prostaglandins E1, E2 and E3 in frog tissue

A method was developed for quantitative determination of endogenous production of prostaglandin (PG)E1, PGE2 and PGE3 by Rana temporaria lung, heart and urinary bladder homogenates, since these tissues contain the precursors, 8,11,14-eicosatrienoic, arachidonic and 5,8,11,14,17-eicosapentaenoic acids. Following homogenization and shaking at 22 degrees C for 30 min, media were extracted by XAD-2, treated with sodium hydroxide in order to convert PGE compounds into PGB compounds, purified by thin-layer chromatography, and analyzed by high-performance liquid chromatography with homo-PGE1 as an internal standard. The ratio of prostaglandins E1, E2 and E3 compared to the ratio of fatty acid precursors in tissue suggested that the tissue content of precursor is not the only factor determining the type of prostaglandin synthesized.

Attenuated cardiovascular effects of prostaglandin I2 and prostaglandin F2 alpha in cold acclimated American bullfrogs, Rana catesbeiana

American bullfrogs, Rana catesbeiana respond to prostaglandins with changes in heart rate and blood pressure. These studies compare responses of warm (22 degrees C) and cold acclimated (5 degrees C) bullfrogs to prostaglandins. Gas chromatographic analysis determined equivalent fatty acid profiles in total lipids of heart and artery tissue from warm and cold acclimated animals. Arachidonic acid was the fatty acid precursor found in greatest abundance in both groups. For cardiovascular experiments, bullfrogs were cannulated by using a T-cannula implanted in the right sciatic artery. In warm acclimated bullfrogs, preinfusion systemic arterial pressure (SAP) was 14.7 +/- 0.5 mm Hg, and heart rate was 33.0 +/- 1.7 beats/min. Cold acclimated bullfrogs had SAP values of 8.0 +/- 0.8 mm Hg, and heart rate was 6.9 +/- 0.3 beats/min. Arachidonic and eicosapentaenoic acid infusions (2,000 micrograms/kg body weight [bw]) were hypertensive in cold acclimated and hypotensive in warm acclimated animals. These effects were blocked by indomethacin (4 mg/kg bw). In both warm and cold acclimated bullfrogs, prostaglandin F2 alpha (3-100 micrograms/kg bw) was hypertensive, while prostaglandin I2 (0.03-3 micrograms/kg bw) was hypotensive, with both prostaglandins stimulating a greater absolute response in warm acclimated animals. In addition, both prostaglandins increased heart rate in warm but not in cold acclimated bullfrogs. The results suggest diminished cardiovascular sensitivity to prostaglandins at low environmental temperatures.

Prostaglandins or prostaglandin like substances are implicated in normal growth and development in oomycetes

The prostaglandin synthesis inhibitors aspirin and indomethacin inhibit the growth of Achlya caroliniana, A. ambisexualis and Saprolegnia parasitica in a dose-related manner. In addition, the inhibitors cause the formation of a characteristic asterisk-shaped colony. This abnormal colony morphology does not appear to be dependent on medium composition, since three different nitrogen and five differentcarbon sources all support the abnormal growth in the presence of 0.1 mM indomethacin. The abnormal colony morphology is the result of abnormal branching. Inhibitor grown colonies are more densely branched than controls, with shorter distances between branches. Inhibited colonies allowed to grow for greater than ten days escape the inhibition and assume a normal gross colony morphology and size, however, they do not reproduce sexually. The addition of 2 micrograms/ml PGF1 alpha to the growth medium partially overcomes the growth inhibition caused by indomethacin. The data suggest a role for prostaglandin or prostaglandin-like compounds in oomycete development.

Comparative effects of prostaglandin E2 and prostaglandin E3 on water flow and cyclic AMP in the urinary bladder of the frog, Rana pipiens

Prostaglandins (PGs) modulate osmotic water flow in amphibian urinary bladders. Gas chromatographic analysis of prostaglandin precursors in bladders showed that arachidonic acid represented 13.0 +/- 0.6% and eicosapentaenoic acid 4.3 +/- 0.1% of the total fatty acid content. The effects of PGE2 and PGE3 on basal and arginine vasotocin (AVT) stimulated water flow were compared. Control water flow (1.1 +/- 0.2 mg/min) was increased to 4.6 +/- 0.3 mg/min with AVT (10(-6)M) present. PGE2 (10(-6)M) inhibited both basal and AVT stimulated water flow. In contrast, PGE3 (10(-6)M) stimulated basal water flow and further increased AVT stimulated water flow. Basal adenylate cyclase activity (ACA, 59 +/- 0.3 pmol cyclic AMP/mg protein/10 min) was stimulated by the addition of AVT in the absence or presence of exogenous guanosine 5' triphosphate (GTP, 10(-5)M). Both PGE2 and PGE3 stimulated basal ACA in the absence, but not in the presence of GTP. In the absence of exogenous GTP, PGE2 increased AVT stimulated ACA, whereas PGE3 decreased it. Both prostaglandins inhibited AVT stimulation when GTP was added. The effects of PGE2, PGE3 and AVT on tissue cyclic AMP levels in whole urinary bladders were similar to the effects seen on ACA in the absence of exogenous GTP. The contrasting effects of PGE2 and PGE3 on control water flow appear distinct from their similar effects on ACA. However, PGE2 and PGE3 may regulate AVT stimulation through mechanisms involving cyclic AMP.

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.