5-HETE: uptake, distribution, and metabolism in MDCK cells

Changes in musculoskeletal structure and function with prolonged bed rest

Prolonged bed rest produces profound changes in muscle and bone, particularly of the lower limb. This review first addresses the various models used by researchers to study disuse-induced changes in muscle and bone as observed during prolonged bed rest in humans. Dramatic change in muscle mass occurs within 4-6 wk of bed rest, accompanied by decreases of 6 to 40% in muscle strength. Immobilization studies in humans suggest that most of this lost muscle mass and strength can be regained with appropriate resistance training within several weeks after a period of disuse. Significant decrements in bone mineral density of the lumbar spine, femoral neck, and calcaneus observed in able-bodied men after bed rest are not fully reversed after 6 months of normal weightbearing activity. Importantly, the lost bone mass is not regained for some weeks or months after muscle mass and strength have returned to normal, further contributing to the risk of fracture. Those who enter a period of bed rest with subnormal muscle and bone mass, especially the elderly, are likely to incur additional risk of injury upon reambulation. Practical implications for exercise professionals working with individuals confined to bed rest are discussed.

Modulation by fish oil diet of eicosanoid-induced anion secretion in the rat distal colon

Eicosanoids are involved in the mediation of inflammatory and allergic processes in the gut. In order to evaluate a potential beneficial effect of the diet, the effect of mediators of inflammation and of a sensitization against egg albumin on anion secretion across the colon was tested using rats fed on a diet containing 15% fish oil as compared to 15% olive oil as donor animals. Feeding on a fish oil diet significantly reduced the response to bradykinin or phospholipase C, known agonist of prostaglandin-induced secretion, by about 50%. The increase in short-circuit current (Isc) induced by the phospholipase A2 stimulator, melittin, or by distension of the gut wall were only insignificantly inhibited by 15-30%. Administration of egg albumin to the mucosas from animals sensitized against egg albumin induced an indomethacin- and tetrodotoxin-sensitive increase in Isc. This response was, however, only insignificantly (30%) reduced by the fish oil diet. In conclusion, the effect of fish oil diet depends on the stimulus used for activation of prostaglandin release. This suggested that different pools of arachidonic acid are differentially affected by the diet or that certain stimuli for phospholipases are strong enough to overcome the effect of a reduced substrate availability. Consequently, a diet rich in polyunsaturated n-3 fatty acids may only play an adjuvant role for the therapy of inflammatory or allergic intestinal diseases.

Removal and restoration of epithelial chloride secretory activity of kinins by gene manipulation

Kinins are known to stimulate electrogenic chloride secretion in many mammalian epithelia, including those of the airways and the alimentary tract. In this study the chloride secretory activity of lysylbradykinin (LBK) on murine colonic epithelium has been examined, specifically to discover the primary and final effector mechanisms in this process, i.e., which kinin receptors are involved and which chloride channels are responsible for chloride secretion. The approach used was to modify the mice genetically and assess the effects on kinin mediated chloride secretion using voltage clamping at zero potential. Briefly, LBK increased SCC in mouse colon by approximately 150 microA cm-2 with an EC50 of approximately 5 nM. In null CF mice LBK, 1 microM had no effect on chloride secretion, but reduced SCC due to K+ secretion. This effect is normally masked in wild-type tissues by dominant chloride secretion, but can be shown to occur to the same extent by measuring K+ secretion with radioisotopes. Null CF mice produce no cftr, but CFTR was introduced into CF mice by injecting a YAC containing the human CF gene into the pronucleus of CF zygotes. Colonic epithelia from mice with the incorporated YAC showed the same sensitivity to LBK as wild-type tissues and achieved the same maximal chloride secretory response. Colonic epithelia from mice in which the B2r gene had been disrupted showed no response to LBK at normally supramaximally effective concentrations, although responses to other secretagogues were normal. Similarly des-Arg-BK caused no acute chloride secretory response in colonic epithelia from B2 knockout mice, however small responses appeared if tissues were incubated in vitro for 3-6 h. It is concluded that cftr chloride channels and B2rs are required for electrogenic chloride secretion. Further CFTR can replace cftr with no effect on either the sensitivity or extent of chloride secretion. In vitro, colonic epithelia may generate B1rs which, upon activation, have a minor effect on chloride secretory activity.

Salt-sensitive hypertension in (mREN-2)27 transgenic rats

The (mREN-2)27 transgenic model of hypertension was developed to investigate the effect of genetic over activity of angiotensin II systems as a contributing factor in the development of arterial hypertension. In this model, transgene-positive rats demonstrate elevated renin-angiotensin system activity not only in the circulatory system but also in adrenal gland, reproductive organs, and brain. Since evidence indicates that angiotensin peptides and osmotic stimuli interact synergistically to produce exaggerated behavioral, endocrine, and cardiovascular effects, we examined the effect of salt consumption on arterial pressure, plasma vasopressin, and body fluid balance in male (mREN-2)27 transgene-positive and -negative rats. Four days of drinking 2% NaCl increased mean arterial pressure from 165 +/- 10 to 199 +/- 7 mm Hg in transgene-positive rats. In contrast, transgene-negative rats showed no change in arterial pressure (126 +/- 5 to 128 +/- 3 mm Hg). Plasma vasopressin levels were significantly elevated only in transgene-positive rats, whereas pituitary levels of vasopressin were significantly lower in transgene-positive rats compared with transgene-negative controls (18 +/- 3 and 118 +/- 14 ng, respectively). Although transgene-positive rats consumed significantly more 2% NaCl than did transgene-negative rats, during this period 24-hour sodium balance did not differ between the groups. Since fluid and electrolyte balance is similar between the two groups of rats, the data suggest that transgene-positive rats may be more sensitive to the effects of increased NaCl intake in terms of both endocrine and cardiovascular responses.

Mediators of inflammation in chronic inflammatory bowel disease

A distinguishing feature of inflammatory bowel disease (IBD) is its apparently spontaneous, chronic relapsing course. Despite extensive research over several decades the etiology of IBD remains unknown, but evidence has accumulated to suggest that the mucosal inflammatory response may be caused by (i) a defective mucosal barrier function resulting in an abnormally increased exposure to luminal antigens and toxins, (ii) an appropriate immunologic response to an unusual infection, antigen or toxin, or (iii) an inappropriate immunological response to ubiquitous antigens or stimuli. In recent years, the identification of established and potential mediators of inflammation has expanded to include eicosanoids, platelet activating factor, biogenic amines, kinins, complement-derived peptides, chemotactic peptides, cytokines, neuropeptides, and reactive metabolites of oxygen and nitrogen. Thus, the study of the inflammatory process has become ever more complex. Until the predisposing and trigger factors have been identified the achievement of a more rational and effective approach to therapy in IBD relies on interruption of the mechanisms responsible for excess mediator formation. As summarized in this review on the role of soluble mediators of inflammation, several Danish gastroenterologists have been profoundly engaged in basic and clinical research in the past 25 years to place some pieces of the confusing puzzle of IBD.

Acclimation to low temperature is associated with an increase in long-chain acyl-CoA synthetase in rainbow trout (Oncorhynchus mykiss) heart

Rainbow trout (Oncorhynchus mykiss) were acclimated to 5 and 15 °C. Uptake of radiolabelled palmitate by isolated cardiomyocytes was linear for at least 65 min. Myocytes from fish acclimated to 5 °C and tested at 5 °C showed higher rates of uptake than those from fish acclimated to 15 °C and tested at 5 °C. There was no significant difference in fatty acid uptake between myocytes from fish acclimated to 5 and 15 °C and tested at their respective acclimation temperature. Acclimation temperature had no effect on levels of intracellular fatty acid binding protein or carnitine palmitoyltransferase. However, acclimation to low temperature resulted in a twofold enhancement in fatty acyl-CoA synthetase activity, which increased in a linear fashion over a 28-day period. An increase in fatty acyl-CoA synthetase, which occurs on the outer mitochondrial membrane and the endoplasmic reticulum, is possibly related to low temperature-induced changes in fatty acid oxidation and synthesis of complex lipids.

Eicosanoids and histamine mediate C5a-induced electrolyte secretion in guinea pig ileal mucosa

C5a is a biologically active polypeptide formed during the course of complement activation and is known to possess histamine-releasing and neutrophil chemotactic properties. In the present study, we have demonstrated that C5a can regulate electrolyte transport across guinea pig ileum, and we have investigated its mechanism of action. Segments of ileum stripped of longitudinal muscle were mounted in Ussing chambers (Krebs' buffer, 37 degrees C, 95% O2/5% CO2) for monitoring short-circuit current (Isc). Serosal application of C5a evoked a transient increase in Isc with an EC50 value of 5.0 nM indicating a potent effect. The C5a-induced increase in Isc was abolished by elimination of both Cl- and HCO3- from the Krebs' solution. Pretreatment with the cyclooxygenase inhibitor indomethacin (5 microM), the neurotoxin tetrodotoxin (0.5 microM) and the H1 receptor antagonist pyrilamine (0.5 microM) reduced the effect of C5a, but the muscarinic antagonist atropine (0.5 microM) was without effect. C5a (100 nM) also evoked the release of histamine (measured by radioimmunoassay in the serosal bathing fluid) by 282% of the control value. In conclusion, in the guinea pig ileum C5a stimulates mucosal anion secretion by releasing histamine and cyclooxygenase products of arachidonic acid. The response is also mediated, in part, via non-chloinergic enteric nerves.

Bradykinin modulates mucin secretion but not synthesis from an intestinal goblet cell line

The effect of the inflammatory mediator bradykinin on glycoprotein synthesis and mucin secretion in the human colonic adenocarcinoma cell line HT29-18N2 was examined. Bradykinin, at a threshold of 0.01 microM, accelerated the rate of mucin discharge as assessed by a mucin-specific ELISA. Using immunofluorescence microscopy, a thick meshwork of extracellular mucus was observed over bradykinin-treated monolayers but not mock-treated controls. Morphometric analysis of bradykinin-treated monolayers revealed no decreases in intracellular mucin stores or any other easily discernable morphological alteration. The ability of the cyclooxygenase inhibitors indomethacin and naproxen to decrease the response to bradykinin by approximately 68% indicates the effect is mediated, at least partially, through the generation of prostaglandins. Bradykinin did not alter the rate of incorporation of 3H-glucosamine into newly synthesized glycoproteins. Bradykinin-accelerated mucin secretion may be linked to the depletion of intracellular mucin stores in the inflammatory bowel disease ulcerative colitis.

Differential regulation of brain angiotensin II in genetically hypertensive and normotensive rats after nephrectomy

To investigate the role of tissue angiotensin II (Ang II) in the maintenance of hypertension after nephrectomy in spontaneously hypertensive rats (SHR), Ang II levels were measured in various tissues of both 12-week-old SHR and normotensive control, Wistar-Kyoto rats (WKY), 48 h after nephrectomy or sham operation. Ang II was determined by radioimmunoassay coupled with high performance liquid chromatography. Nephrectomy caused a decrease of plasma renin activity and plasma Ang II concentration in both SHR and WKY. Aortic Ang II levels were significantly lowered by nephrectomy only in WKY, and not in SHR. Ang II levels in hypothalamic block, brainstem and cerebellum of SHR increased after nephrectomy, whereas those of WKY were unchanged. Intracerebroventricular administration of ceronapril, an angiotensin converting enzyme inhibitor, significantly decreased sustained high blood pressure in SHR 48 h after nephrectomy compared with vehicle administration, whereas intravenous administration had no effect. These results suggest that in spite of the important role of the renal renin-angiotensin system in maintenance of high blood pressure in SHR, control mechanisms may switch to other systems after nephrectomy, and that the increased brain Ang II levels after nephrectomy may be related to these mechanisms.

Requirement of human renal water channel aquaporin-2 for vasopressin-dependent concentration of urine

Concentration of urine in mammals is regulated by the antidiuretic hormone vasopressin. Binding of vasopressin to its V2 receptor leads to the insertion of water channels in apical membranes of principal cells in collecting ducts. In nephrogenic diabetes insipidus (NDI), the kidney fails to concentrate urine in response to vasopressin. A male patient with an autosomal recessive form of NDI was found to be a compound heterozygote for two mutations in the gene encoding aquaporin-2, a water channel. Functional expression studies in Xenopus oocytes revealed that each mutation resulted in nonfunctional water channel proteins. Thus, aquaporin-2 is essential for vasopressin-dependent concentration of urine.

15-HETE: selective incorporation into inositol phospholipids of MDCK cells

The interaction of 15-hydroxyeicosatetraenoic acid (15-HETE) and cultured MDCK renal tubular epithelial cells was investigated to determine whether incorporation of this lipoxygenase product will affect polyphosphoinositide formation. MDCK cells were incubated with 1 microM [3H]-15-HETE for 15 to 120 minutes. Maximum uptake occurred between 15 and 30 minutes, and after 60 minutes, 70% of the incorporated 15-HETE was present in the phosphatidylinositol (PI) fraction. Some 15-HETE was also incorporated into phosphatidylinositol-4-monophosphate (PIP) and phosphatidylinositol-4,5-bisphosphate (PIP2). However, even though more 15-HETE than arachidonic acid was incorporated into PI, the fractional amount of 15-HETE present in the polyphosphoinositides was smaller than arachidonic acid. Therefore, although 15-HETE is selectively channeled into PI, conversion of PI species containing 15-HETE to PIP and PIP2 is relatively impaired. This suggests that either PI containing 15-HETE is a less effective substrate for phosphorylation, or PI containing arachidonic acid is a preferred substrate. MDCK cells converted 15-HETE to polar metabolites that were released into the extracellular fluid. This process may constitute a renal tubular mechanism for the clearance of 15-HETE and related lipoxygenase products.

Rapid increase in mitochondrial volume in nucleus magnocellularis neurons following cochlea removal

Second-order auditory neurons in nucleus magnocellularis (NM) of the chick brainstem undergo a series of rapid metabolic changes following unilateral cochlea removal, culminating in the death of 25% of NM neurons. Within hours of cochlea removal, ipsilateral NM neurons show marked increases in histochemical staining for the mitochondrial enzymes succinate dehydrogenase and cytochrome oxidase. We investigated corresponding ultrastructural changes in NM neurons by preparing animals undergoing unilateral cochlea removal for transmission electron microscopy. We quantified changes in NM mitochondrial volume by stereological methods and qualitatively compared mitochondrial morphology between NM neurons destined to survive and those destined to die after cochlea removal. Within hours of cochlea removal, ipsilateral NM neurons show striking increases in mitochondrial volume (84% at 6 hours and 236% at 12 hours after cochlea removal compared to unoperated, control animals). At 2 week survival times, ipsilateral NM neurons contain fewer mitochondria than contralateral neurons. Surprisingly, anesthesia alone causes short-term increases in NM mitochondrial volume. Animals anesthetized with pentobarbital and ketamine and sacrificed 6 or 12 hours later showed a 45% increase in mitochondrial volume compared to previously unanesthetized animals. NM neurons destined to die within days of cochlea removal can be identified within several hours after deafferentation by the appearance of their ribosomes. We observed qualitative differences in mitochondrial morphology in dying neurons. Mitochondria in neurons destined to die consistently showed mitochondrial swelling and vacuolization indicative of metabolic dysfunction. Similar mitochondrial changes have been reported when mitochondria take up excess calcium. Ultrastructural changes in NM after cochlea removal display features of both programmed and pathological cell death, in which increased intracellular calcium is thought to play a role.

Type 2 (non-insulin-dependent) diabetes mellitus associated with a mutation of the glucokinase gene in a Japanese family

Mutations were screened for in the glucokinase gene of 25 Japanese patients with Type 2 (non-insulin-dependent) diabetes mellitus. Each exon was scanned by electrophoresis of enzymatically amplified DNA segments under non-denaturing conditions and variants were sequenced. A variant pattern was detected in exon 5 of one patient. Direct sequencing of this exon revealed a single nucleotide substitution in codon 188 (GCT-->ACT) of one of two alleles resulting in the mutation of Ala188-->Thr, an invariant residue in the sequence of all mammalian glucokinases and hexokinases. This mutation was not found in 40 normal control subjects. The proband had been diagnosed with Type 2 diabetes at the age of 62 years. Four other members of her family have the same mutation and all have Type 2 diabetes or impaired glucose tolerance. The youngest age at diagnosis of Type 2 diabetes in these other members was 13 years, suggesting that her pedigree was maturity-onset diabetes of the young (MODY). All subjects with the Thr188 mutation show a decreased insulin secretory response during oral glucose tolerance testing. Mutations in the glucokinase gene associated with Type 2 diabetes have been previously identified in Caucasian (French and British) subjects. This study indicates that mutations in this gene are also implicated in the development of Type 2 diabetes in Asians. Further studies are required to determine the frequency of mutations in glucokinase among Japanese patients with Type 2 diabetes.

Plasma levels of parathyroid hormone, vitamin D, calcitonin, and calcium in association with endurance exercise

Nine male marathon runners were investigated during habitual training (week 0), after 3 weeks of training break (week 3), and after 2 weeks (week 5) and 4 weeks (week 7) of retraining. Maximal oxygen uptake, body fat (BF), and plasma levels of 25(OH)D3, 1,25(OH)2D3, parathyroid hormone (PTH), calcitonin (CT), albumin, and albumin-corrected calcium were determined throughout weeks 0-7. The maximal oxygen uptake decreased after training break and increased during retraining (P = 0.002). BF did not change significantly. Plasma 1,25(OH)2D3 was elevated after training break and decreased after 2 and 4 weeks of retraining [week 0: 44.0 +/- 3.7 (SEM) pg x 1(-1); week 3: 52.4 +/- 6.0 pg x 1(-1); week 5: 42.0 +/- 2.8 pg x 1(-1); week 7: 36.9 +/- 2.3 pg x 1(-1); P = 0.03]. Plasma 25(OH)D3 did not change significantly. Plasma PTH increased throughout the training break and retraining (week 0: 1.36 +/- 0.25 pmol x 1(-1); week 3: 2.02 +/- 0.43 pmol x 1(-1); week 5: 2.23 +/- 0.60 pmol x 1(-1); week 7: 2.63 +/- 0.34 pmol x 1(-1); P = 0.03). Albumin-corrected calcium values were transiently decreased during retraining (week 3: 2.77 +/- 0.08 mM; week 5: 2.47 +/- 0.05 mM; week 7: 2.66 +/- 0.07 mM; P = 0.01). Plasma CT did not change during training break, but was transiently decreased during retraining (week 0: 9.97 +/- 0.39 pmol x 1(-1); week 3: 9.91 +/- 0.37 pmol x 1(-1); week 5: 8.19 +/- 0.50 pmol x 1(-1); week 7: 9.02 +/- 0.45 pmol x 1(-1); P = 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

A human epithelial cell line, intestine 407, can produce 5-hydroxyeicosatetraenoic acid and leukotriene B4

The present study was carried out to further characterize the role of non-inflammatory cells in the inflammatory process. More specifically, we have investigated whether human epithelial cells can generate inflammatory lipid mediators via activation of the 5-lipoxygenase pathway. The cells were stimulated with the calcium ionophore A23187 (5 microM) for different periods of time, after which the production of eicosanoids was determined by gradient reverse-phase high performance liquid chromatography (RP-HPLC) and rapid spectral detection, permitting continuous ultraviolet spectroscopy. In both non-prelabeled cells and cells prelabeled with [1-14C]arachidonic acid, cell stimulation for 30 min or more resulted in the production of two important 5-lipoxygenase products: 5-hydroxyeicosatetraenoic acid (5-HETE) and leukotriene B4 (LTB4). Stimulation for 15 min or less, however, led solely to the formation of 5-HETE. The identities of 5-HETE and LTB4 were confirmed by HPLC retention times and UV spectra, as well as by gas chromatography-mass spectrometry for 5-HETE and radioimmunoassay for LTB4. It can therefore be concluded that human epithelial cells in general can produce important inflammatory mediators, which suggests that epithelial cells may play a more active role in the inflammatory process than is normally assumed.

Epithelial secretory response to inflammation

As suggested by this and previous reviews, the neuroimmunoregulation of intestinal secretion is a complex series of endocrine, neurocrine, paracrine and autocrine interactions between the underlying cells in the mucosa and submucosa and the intestinal enterocyte. Under normal conditions, the balance of each of these systems is delicately controlled, thus allowing for normal, consistent intestinal function. However, when this finely-tuned system is altered, such as in a diseased state, the resultant effect is an amplification of the host defense response. Initially thought to be protective against further insult, this local immune response, if allowed to continue uncontrollably, can exacerbate the disease process.

Metabolism of arachidonic acid by isolated rabbit ciliary epithelium

We examined the ability of rabbit ciliary epithelium to metabolize arachidonic acid in vitro. The epithelium was homogenized and incubated with 14C-labeled arachidonic acid. 14C-labeled metabolites were extracted and then separated by thin layer chromatography. The range of arachidonic acid metabolites synthesized by ciliary epithelium was compared to the metabolites generated by rabbit iris-ciliary body. Ciliary epithelium produced substantial amounts of arachidonic acid metabolites that comigrated with 5-HETE and 12-HETE. Authenticity of the 12-HETE produced by ciliary epithelium was confirmed by gas chromatography/mass spectrometry. The ciliary epithelium generated only small amounts of the cyclooxygenase products, PGF2 alpha, PGE2, PGD2 and 6k-PGF1 alpha. In contrast, the iris-ciliary body produced large amounts of cyclooxygenase products such as PGF2 alpha and PGD2. The ability of the ciliary epithelium to generate 12-HETE is noteworthy since 12(R)-HETE is known to be capable of lowering intraocular pressure.

Appearance of water channels in Xenopus oocytes expressing red cell CHIP28 protein

Water rapidly crosses the plasma membrane of red blood cells (RBCs) and renal tubules through specialized channels. Although selective for water, the molecular structure of these channels is unknown. The CHIP28 protein is an abundant integral membrane protein in mammalian RBCs and renal proximal tubules and belongs to a family of membrane proteins with unknown functions. Oocytes from Xenopus laevis microinjected with in vitro-transcribed CHIP28 RNA exhibited increased osmotic water permeability; this was reversibly inhibited by mercuric chloride, a known inhibitor of water channels. Therefore it is likely that CHIP28 is a functional unit of membrane water channels.

Differential metabolism of hydroxyeicosatetraenoic acid isomers by mouse cerebromicrovascular endothelium

Hydroxyeicosatetraenoic acid (HETE) derivatives of arachidonic acid are produced in the brain and have been implicated as pathologic mediators in various types of brain injury. To understand better their fate in the brain, particularly in cerebral microvessels, several HETEs were incubated with cultured mouse cerebromicrovascular endothelium for 1, 2, and 4 h, followed by HPLC analysis of medium and cellular lipids. 5(S)-, 8(RS)-, and 9(RS)-HETE were not metabolized by the cells, but were extensively incorporated, unmodified, into cell lipids. On the other hand, 11(RS)-, 12(S)-, and 15(S)-HETE were extensively metabolized and only minimally incorporated into cell lipids. Previously, the major 12-HETE metabolite was identified as 8-hydroxyhexadecatrienoic acid. In the present study, we identified the major 11-HETE metabolite as 7-hydroxyhexadecatrienoic acid and the major 15-HETE metabolite as 11-hydroxyhexadecatrienoic acid. omega-3 compounds, 15(S)- and 12(S)-hydroxyeicosapentaenoic acids (HEPE), were also metabolized to more polar compounds, but to a lesser extent than their tetraenoic acid, omega-6 counterparts. Comparison of 5-, 12-, and 15-HETE enantiomers revealed no differences in metabolism or incorporation between the R and S stereoisomers. These data suggest that many isomers of HETE and HEPE can be incorporated into cell lipids or metabolized by pathways that do not distinguish between enantiomers. These pathways, however, are sensitive to the position or number of double bonds and are selective based on the position of the hydroxyl group.

Action of bradykinin at the cyclooxygenase step in prostanoid synthesis through the arachidonic acid cascade

Bradykinin enhances prostanoid synthesis in aorta smooth muscle cells. Free arachidonic acid also enhances prostanoid synthesis and bradykinin, unlike fatty acid releasing agents, has a synergistic effect with free arachidonic acid. Bradykinin promotes metabolite release from cells prelabeled with [14C]-arachidonic acid and this effect is blocked completely by indomethacin. High performance liquid chromatography shows increase amounts of labeled 6-keto-prostaglandin F1 alpha, prostaglandin E2 and three additional cyclooxygenase-dependent metabolites but no increase in free arachidonic acid or other metabolites either in the absence or presence of indomethacin. Fatty acid releasing agents such as A23187 and cyclosporine A have very different effects on cells. These agents enhance levels of prostanoids, a number of other cyclooxygenase-independent metabolites, and free arachidonic acid which is even more elevated with added indomethacin. Bradykinin behaves in all respects like another agent, bacterial lipopolysaccharide, and the action of both agents is consistent with a mechanism involving cyclooxygenase rather than fatty release in the arachidonic acid cascade.

Functional consequences of abnormal fatty acid profiles in cultured airway epithelial cells

Maintenance of serum-free conditions for the culture of TE or other airway epithelial cells provides a defined environment in which to explore the regulation of cellular functions. Yet TE cells appear to be dependent on the medium for essential, if not all, polyunsaturated fatty acids. At present, some laboratories routinely use serum to support the growth of airway epithelial cells, presumably in part through recognition that cells of mammalian origin require an exogenous source of lipids. While 5% FBS can increase the linoleic and arachidonic acid content of cultured rabbit and human TE cells, it does not fully restore the fatty acid composition of cultured TE cells to that of freshly isolated cells, particularly in the case of human TE cells. Equally good, if not better, repair of membrane fatty acid composition can be achieved by addition of a defined, commercial non-serum source of lipids (Excyte III) plus exogenous arachidonic acid. Cultured TE cells maintained in serum-free medium have been shown to be deficient in prostaglandin and HETE production, both at baseline and in response to physiological stimuli compared to TE cells with greater endogenous content of arachidonic acid. Differences between lipid supplemented and unsupplemented cultured TE cells in cAMP response to PGE2 and in susceptibility to hyperoxic injury have been observed. Other cellular functions regulated by the fatty acid composition of membrane lipids may also be impaired in lipid unsupplemented cells. It is evident that the maintenance of as normal as possible membrane fatty acid content is essential to the use of cultured TE cells as experimental models of airway epithelium.

Anatomic and metabolic responses to thermal acclimation in the ninespine stickleback, Pungitius pungitius

Male ninespine sticklebacks, Pungitius pungitius, acclimated to 3°C have higher activities of mitochondrial enzymes in their axial muscles than males acclimated to 20°C. Phosphofructokinase and pyruvate kinase activities tended to be higher in cold than warm acclimated males. For females, warm acclimation tended to decrease only mitochondrial enzyme activities. As thermal acclimation did not change the physical condition and most anatomic parameters of the sticklebacks, the enzymatic changes do not seem due to mobilization of somatic reserves. Field acclimatization to warm temperatures led to a marked decrease in physical condition in both males and females. This decrease in physical condition could largely be attributed to atrophy of the carcass mass. Spring males had higher activities of phosphofructokinase, citrate synthase and cytochrome oxidase in the axial muscle than summer males. Again, females showed a less marked response. These data suggest that environmental temperature is a major determinant of muscle aerobic capacity, at least for male ninespine sticklebacks. Thus, these northern temperate zone fish retain the capacity for thermal compensation, much like their temperate zone counterparts.

Generation of lipoxygenase metabolites of arachidonic acid by monolayer cultures of tracheal epithelial cells and intact tracheal segments from rabbits

We compared the profile of lipoxygenase metabolites of arachidonic acid (AA) generated by cultured rabbit tracheal epithelial (TE) cells with that produced by intact rabbit tracheal segments at baseline and following addition of exogenous AA or calcium ionophore A23187. Lipoxygenase metabolites in effluent media were resolved by high-pressure liquid chromatography and quantitated by radioimmunoassay for monohydroxyeicosanoid (HETE) and leukotriene (LT) metabolites [5-, 12-, and 15-HETE; LTB4, LTC4, LTD4]. Following incubation with exogenous AA (10 micrograms/ml), cultured TE cells generated immunoreactive products that coeluted with authentic 5-, 12-, and 15-HETE standards. 12-HETE was the predominant metabolite. Whereas the generation of HETEs by TE monolayers was dependent on addition of exogenous AA, intact tracheal segments demonstrated a baseline production of 12-HETE and lesser amounts of 5- and 15-HETE as well as unidentified metabolites with UV absorbance at 280 nm. Incubation of tracheal segments with AA resulted in augmented metabolite production. In cultured TE cells, small quantities of HETEs were present intracellularly esterified to membrane phospholipids or free in the cytosol, and significant increases in free cytosolic 12- and 15-HETE were detected postincubation with AA. Calcium ionophore (5 microM) did not induce significant increases in HETE production in either cultured TE cells or tracheal segments. Minimal or no immunoreactive LTs B4, C4, and D4 were produced by TE monolayers or tracheal segments at baseline or following addition of AA or ionophore. Production of HETEs by cultured TE cells was not associated with decreased viability, release of intracellular lactic dehydrogenase, or loss of cells from the monolayers. Preincubation of monolayer cultures or tracheal segments with 5,8,11,14-eicosatetraynoic acid prior to addition of exogenous AA inhibition metabolite production. Our observations provide further documentation for the generation of lipoxygenase metabolites by TE cells and suggest that the array of metabolites generated by cultured TE cells may not be representative of the entire spectrum of AA metabolites produced by intact native epithelium.

Effect of bradykinin on feline gallbladder water transport and prostanoid formation

Continuing evaluation of the pathophysiology of gallbladder disease has demonstrated significant relationships between gallbladder mucosal fluid transport, gallbladder inflammation, and prostanoid formation. Inflamed gallbladder mucosa secretes, rather than absorbs, fluid, a process associated with prostaglandin formation. Bradykinin has been previously implicated in the pathogenesis of cholecystitis and, in the intestine, bradykinin stimulates mucosal fluid secretion by a prostaglandin-mediated mechanism. Bradykinin was infused into the gallbladder lumen and administered intraarterially into the hepatic artery of perfused cat gallbladders. Both methods of bradykinin administration reversed the mucosal absorption present during control experiments as measured by concentration changes in a nonabsorbable marker. Perfusate and gallbladder tissue prostaglandin E concentrations were significantly increased by bradykinin when compared to control values. Concentrations of 6-keto PGF1 alpha in perfusate solutions and in gallbladder tissue were significantly increased, suggesting bradykinin increased prostacyclin formation. Bradykinin administration significantly increased inflammation, as evaluated by a histologic scoring system. Indomethacin was administered intravenously along with luminal perfusion of the gallbladder with bradykinin. Indomethacin significantly decreased gallbladder fluid secretion and prostanoid formation, but not histologic inflammation, when compared to values produced by bradykinin alone. An increase in systemic vascular and bile kinin concentrations produces gallbladder mucosal water secretion, a process which may be mediated by prostanoids. Histologic inflammation produced by bradykinin was not prevented by indomethacin.

Increase in the blood pressure and decrease in the norepinephrine release in the ventrolateral medulla during intraventricular administration of hypertonic NaCl

Norepinephrine (NE) release in the ventrolateral medulla (VLM) was serially measured in anesthetized male Wistar rats during the rise in the blood pressure (BP) produced by acute intraventricular (ICV) administration of hypertonic (1.5 M) NaCl. Catecholamine release was determined by a brain microdialysis method using high performance liquid chromatography and electrochemical detector. The release of NE in the VLM was significantly decreased after ICV 1.5 M NaCl. In another set of rats, the pressor response to acute ICV 1.5 M NaCl was attenuated by selective administration of NE to the VLM using the microdialysis method. Chronic and continuous ICV infusion of 1.5 M NaCl to conscious rats caused an increase in BP on day 10 which was associated with a decrease in NE release in the VLM; concomitant ICV infusion of NE or of a synthetic NE precursor, L-threo-3,4-dihydroxyphenylserine (L-DOPS) prevented the rise in BP as well as the reduction in NE release. These results suggest that a decrease in the NE release of the VLM may contribute to the change in BP induced by ICV infusion of hypertonic saline.