Preferential esterification of endogenously formed 5-hydroxyeicosatetraenoic acid to phospholipids in activated polymorphonuclear leukocytes

The esterification of endogenously formed 5-hydroxyeicosatetraenoic acid (5-HETE) to cellular lipids in rat polymorphonuclear leukocytes (PMNL) was studied quantitatively by a fluorometric method using HPLC. Rapid and maximal production of free 5-HETE was observed after a 5-min stimulation of PMNL with A23187. The amount of free 5-HETE then declined rapidly, while that of 5-HETE esterified to phospholipids and triacylglycerol concomitantly increased in a time-dependent manner. Stimulation by A23187 yielded approximately 100 ng/10(7) cells esterified 5-HETE in 60 min, which corresponded to the decrease in the amount of free 5-HETE from 5 min to 60 min and indicated that free 5-HETE, which was formed endogenously, was metabolized predominantly by esterification to cellular lipids. The esterification profile of exogenous 5-HETE was different from that of endogenous 5-HETE. 5-[3H]HETE, which was added exogenously to the culture medium, was rapidly incorporated into PMNL and almost 80% of the total radioactivity was located in triacylglycerol. A quantitative study revealed that endogenous 5-HETE was esterified equally to phospholipids and triacylglycerol. Like PMNL, peritoneal macrophages treated with A23187 released significant amounts of 5-HETE. However, less 5-HETE was esterified to cellular lipids than in PMNL. Negligible amounts of 12-HETE, produced by activated peritoneal macrophages or activated platelets after a challenge with A23187, were esterified during the entire incubation. Exogenous 5-HETE was rapidly taken up by PMNL, but was incorporated into macrophages much more slowly than into PMNL. No uptake of 12-HETE into macrophages was observed. The rapid uptake of exogenous 5-HETE was strongly inhibited by the suppression of acylation of 5-HETE by triacsin C. These results suggest that esterification might be one of the factors that regulate the rate of incorporation of 5-HETE.

Quantitation of monohydroxy fatty acids by high-performance liquid chromatography with fluorescence detection

A high-performance liquid chromatographic (HPLC) procedure for the separation of hydroxyeicosatetraenoic acids (HETEs) and hydroxyoctadecanoic acids (HODEs) after derivatization of the hydroxy group with 1-anthroylnitrile is described. Anthroyl esters of HETEs were separated from those of HODEs by reversed-phase HPLC. The positional isomers of the HETEs and HODEs were well separated by normal-phase HPLC. The fluorimetric HPLC method has a high sensitivity and naturally occurring HETEs can be quantitatively analyzed at the picomolar level. The amount of 5-HETE in A23187-stimulated polymorphonuclear leukocytes (PMNLs) was determined by the present method. PMNLs produced approximately 150 ng of 5-HETE per 10(7) cells at 5 min stimulation. The amount of 5-HETE determined by fluorimetric detection was consistent with that determined by ultraviolet detection (235 nm).

Generation of affinity for antithrombin III by supplemental sulfation of heparin species with low affinity for the protein

The tributylammonium salt of a porcine heparin subfraction with low affinity for antithrombin III (Mr 7,500-18,000; anti-clotting activity, 7 USP units/mg), having degrees of sulfate substitution at D-glucosamine and L-iduronic acid residues of GlcNS 0.786, GlcN6s 0.628, and IdoA2s 0.682 mol, was reacted with 10 or 20 mol of pyridine-sulfur trioxide per mol equiv. of available hydroxyl groups in N,N-dimethylformamide at -10 degrees C for 1 h. Both chemical and NMR spectroscopic analyses revealed that sulfation proceeded exclusively at HO-6 in D-glucosamine and HO-2 in L-iduronic acid residues, according to the amount of the sulfating reagent used (GlcNS: 0.825, 0.830; GlcN6s: 0.872, 0.928; IdoA2s: 0.687, 0.749 mol, respectively). Affinity chromatography of the sulfated products on antithrombin III-Sepharose gel indicated that the polysaccharide acquired some affinity for the protein following the sulfation, as shown by the increase in the proportion of the high-affinity heparin fraction (%) from 1.1 to 6.7. Biological examination of these products indicated that sulfation at natural positions along with the polysaccharide chain resulted in significant increases in all the activities (blood anti-clotting, anti-Factor IIa, and anti-Factor Xa), and in the strength of intrinsic fluorescence of antithrombin III.

Contribution of chemical 6-O-sulfation of the aminodeoxyhexose residues in whale heparin with high affinity for antithrombin III to its anticoagulant properties

The tributylammonium salt of whale (Balaenoptera borealis L.) intestinal heparin with high affinity for antithrombin III, whose degrees of sulfate-substitution in D-glucosamine and L-iduronic acid residues are GlcNS 0.738, GlcN6S 0.384, and IdoA2S 0.510 mol, was reacted with 2.5, 5.0, or 10.0 mol of pyridine-sulfur trioxide/mol of available hydroxyl groups in N,N-dimethylformamide at -10 degrees C for 1 h. Both chemical and NMR spectroscopic analyses revealed that an exclusive 6-O-sulfation of the D-glucosamine residues proceeded, according to the amount of the sulfating reagent used (GlcN6S: 0.476, 0.585, and 0.641 mol, respectively), the degree of sulfation at other natural substitution positions in the polysaccharide being unchanged, without any detectable unnatural sulfate-substitution. Biological examination of these products indicated that the 6-O-sulfation in the original whale heparin resulted in significant increases in blood clotting and anti-Factor IIa activities (maximal 43 and 82% increases, respectively), and in a moderate increase in the ability to bind antithrombin III, that is, in anti-Factor Xa activity and in intrinsic fluorescence enhancement of the protein (maximal 28 and 30% increases, respectively), together with a maximal 10% increase in the proportion of heparin species with higher affinity for antithrombin III, released with 1.0-3.0 M NaCl from antithrombin III-Sepharose.