Effects of two different dietary sources of long chain omega-3, highly unsaturated fatty acids on incorporation into the plasma, red blood cell, and skeletal muscle in horses.

The objective of this study was to examine the effects of different sources of dietary omega-3 (n-3) fatty acid supplementation on plasma, red blood cell, and skeletal muscle fatty acid compositions in horses. Twenty-one mares were blocked by age, BW, and BCS and assigned to 1 of 3 dietary treatments with 7 mares per treatment. Dietary treatments were: 1) control or no fatty acid supplement (CON), 2) 38 g of n-3 long chain, highly unsaturated fatty acid (LCHUFA) supplement/d provided by algae and fish oil (MARINE) containing alpha-linolenic acid (ALA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA), and 3) 38 g of n-3 LCHUFA supplement/d provided by a flaxseed meal (FLAX) containing ALA. Each supplement was added to a basal diet consisting of hay and barley and was fed for 90 d. Blood samples and muscle middle gluteal biopsies were taken at d 0, 30, 60 and 90 of supplementation. Plasma, red blood cell and skeletal muscle fatty acid profiles were determined via gas chromatography. Plasma linoleic acid (LA) and ALA were at least 10 and 60% less (P < 0.01), respectively, in the MARINE compared with the FLAX and CON groups. Plasma EPA and DHA were only detected in the MARINE group, and EPA increased 40% (P < 0.001) from d 30 to 60, and DHA 19% (P < 0.01) from d 30 to 90. Red blood cell LA and ALA were not different among treatments. Red blood cell EPA and DHA were only detected in the MARINE group, where EPA increased 38% (P < 0.01) from d 30 to 60, and DHA increased 56% (P < 0.001) between d 30 and 90. Skeletal muscle LA was at least 17% less (P < 0.001) in the MARINE group compared with the other treatments. Skeletal muscle ALA was 15% less (P = 0.03) in the MARINE group compared with FLAX and CON groups. Skeletal muscle EPA was at least 25% greater (P < 0.001) in MARINE group compared with other treatments and increased (P < 0.001) by 71% from d 30 to 60. Skeletal muscle DHA was at least 57% greater (P < 0.001) in the MARINE group compared with other groups and increased (P < 0.001) by 40% between d 30 and 90. As far as the authors are aware, this is the first study to demonstrate that dietary fatty acid supplementation will affect muscle fatty acid composition in horses. Incorporation of n-3 LCHUFA into blood and muscle depends directly on dietary supply of specific fatty acids.

Suppression of cyclooxygenase-2 and inducible nitric oxide synthase expression by conjugated linoleic acid in murine macrophages.

Activated macrophages express inducible isoforms of cyclooxygenase (COX-2) and nitric oxide synthase (iNOS), and produce excessive amounts of prostaglandin E(2) (PGE(2)) and nitric oxide (NO) which play key roles in cancer pathogenesis. Conjugated linoleic acid (CLA) is an anticarcinogen while arachidonic acid (AA) may be a procarcinogen by increased PGE(2) production. This study examined the effects of CLA and AA on PGE(2) and NO synthesis in endotoxin-activated macrophages. RAW264.7 macrophages were incubated in medium containing no added lipid (control), 30 microM AA (AA medium), or 30 microM CLA (CLA medium) for 24 h followed by activation with bacterial endotoxin lipopolysaccharide (LPS; 100 ng/ml) for 9 h. CLA significantly depressed PGE(2) and NO production by 78% (P=0.003) and 57% (P=0.0001) respectively. Northern blot analysis of COX-2 and iNOS showed significant 33% (P=0.01) and 51% (P=0.04) decreases, respectively, paralleling those seen for PGE(2) and NO production. In contrast, AA significantly increased PGE(2) synthesis by 62% (P=0.02) and also suppressed NO production and iNOS expression in the same manner as observed for CLA. These results suggest that the anticarcinogenic effect of CLA in endotoxin-activated macrophages may be related to its ability to decrease both PGE(2) and NO synthesis by suppressing transcription of COX-2 and iNOS.

Effects of conjugated linoleic acids and docosahexaenoic acid on rat liver and reproductive tissue fatty acids, prostaglandins and matrix metalloproteinase production.

Long chain n-6 and n-3 fatty acids play important roles in labor and delivery. These effects may be mediated by prostaglandin (PG) synthesis and by regulation of matrix metalloproteinases (MMPs), both of which play roles in uterine contraction, cervical ripening and rupture of fetal membranes. The effects of altering dietary n-6:n-3 long chain fatty acid ratios, and the addition of dietary conjugated linoleic acids (CLA) and docosahexaenoic acid (DHA) on fatty acid composition of reproductive tissues, PG synthesis in liver and reproductive tissue and serum MMP levels were examined in pregnant rats. Modified AIN-96G diets with n-6:n-3 ratios of 7:1 and 34:1 with and without added 1.1% (by weight) conjugated linoleic acid (CLA) and/or 0.3% (by weight) DHA were fed through day 20 of gestation. Reproductive tissues readily incorporated both DHA and CLA. CLA significantly (P<0.05) depressed PGF(2 alpha)synthesis in placenta, uterus and liver by 50% when the n-6:n-3 ratio was 7:1 and by 66% at 34:1 ratio. Significant differences (P<0.05) in PGE(2)synthesis in uterus and liver were seen only between groups fed the high ratio of n-6:n-3 without CLA, and the low ratio with CLA. Addition of CLA to DHA containing diets depressed PGF(2alpha) by one-third in uterus and liver (P<0.05). Serum MMP-9 and active MMP-2 were suppressed (P<0.05) by addition of either CLA or DHA.

The role of n-3 fatty acids in gestation and parturition.

Preterm birth is the most common cause of low infant birth weight and infant morbidity and mortality. Evidence from human and animal studies indicates that essential fatty acids of both the n-3 and n-6 series, and their eicosanoid metabolites, play important and modifiable roles in gestational duration and parturition, and n-3 fatty acid intake during pregnancy may be inadequate. Prostaglandins (PG) of the 2-series are involved in parturition and connective tissue remodeling associated with cervical maturation and rupture of membranes. In the absence of infections, preterm birth is characterized by lower reproductive tissue PG production and decreased inducible cyclooxygenase expression. Women who deliver prematurely have increased pools of n-6 fatty acid and decreased n-3 fatty acids, despite the lower PG production. Several human pregnancy supplementation trials with n-3 fatty acids have shown a significant reduction in the incidence of premature deliver and increased birth weight associated with increased gestational duration. Supplementation with long chain n-3 fatty acids such as docosahexaenoic acid may be useful in prolonging the duration of gestation in some high-risk pregnancies. Evidence presented in this review is discussed in terms of the roles of dietary n-3 and n-6 fatty acids in gestation and parturition, mechanisms by which they may influence gestational duration and the human trials suggesting that increased dietary long-chain n-3 fatty acids decrease the incidence of premature delivery.

Dietary ratio of (n-6)/(n-3) polyunsaturated fatty acids alters the fatty acid composition of bone compartments and biomarkers of bone formation in rats.

The effects of dietary polyunsaturated fatty acids (PUFA) on ex vivo bone prostaglandin E(2) (PGE(2)) production and bone formation rate were evaluated in rats. Weanling male Sprague-Dawley rats were fed AIN-93G diet containing 70 g/kg of added fat for 42 d. The dietary lipid treatments were formulated with safflower oil and menhaden oil to provide the following ratios of (n-6)/(n-3) fatty acids: 23.8 (SMI), 9.8 (SMII), 2.6 (SMIII), and 1.2 (SMIV). Ex vivo PGE(2) production in liver homogenates and bone organ cultures (right femur and tibia) were significantly lower in rats fed diets with a lower dietary ratio of (n-6)/(n-3) fatty acids than in those fed diets with a higher dietary ratio. Regression analysis revealed a significant positive correlation between bone PGE(2) and the ratio of arachidonic acid (AA)/eicosapentaenoic acid (EPA), but significant negative correlations between bone formation rate and either the ratio of AA/EPA or PGE(2) in bone. Activities of serum alkaline phosphatase isoenzymes, including the bone-specific isoenzyme (BALP), were greater in rats fed a diet high in (n-3) or a low ratio of (n-6)/(n-3), further supporting the positive action of (n-3) fatty acids on bone formation. These results demonstrated that the dietary ratio of (n-6)/(n-3) modulates bone PGE(2) production and the activity of serum BALP in growing rats.

Modulation of MCF-7 breast cancer cell signal transduction by linoleic acid and conjugated linoleic acid in culture.

The effects of modifying membrane fatty acid composition on cell growth, phospholipase C (PLC) and protein kinase C (PKC) activities, and prostaglandin E2 (PGE2) secretion were investigated. Hormone responsive MCF-7 human breast cancer cells were incubated in a serum-free medium containing epidermal growth factor and supplemented with physiologic concentrations (0.18-1.78 x 10(-5) M) of linoleic acid (LA) or conjugated linoleic acid (CLA). Linoleic acid stimulated cancer cell growth, while CLA was inhibitory. Supplementation with LA or CLA altered cell membrane composition. Linoleic acid stimulated PLC activity with or without GTP gamma (S), and tended to increase membrane PKC activity. However, CLA supplementation did not modify membrane PLC or PKC activity. Prostaglandin E2 secretion was not influenced by LA or CLA. These data show that growth inhibition by CLA was not mediated through PLC-, PKC- or PGE2-dependent signal transduction pathways, suggesting that another inhibitory mechanism may be involved. Although biological differences appeared to be modest (5-20% of control), the fact that LA and CLA treatment resulted in significant biological effects at physiologic concentrations is relevant, since most human cancers require years to develop.

Omega-3 fatty acids enhance ligament fibroblast collagen formation in association with changes in interleukin-6 production.

Altering dietary ratios of n-3 and n-6 polyunsaturated fatty acids (PUFA) represents an effective nonpharmaceutical means to improve systemic inflammatory conditions. An effect of PUFA on cartilage and bone formation has been demonstrated, and the purpose of this study was to determine the potential of PUFA modulation to improve ligament healing. The effects of n-3 and n-6 PUFA on the in vitro healing response of medial collateral ligament (MCL) fibroblasts were investigated by studying the cellular coverage of an in vitro wound and the production of collagen, PGE2, IL-1, IL-6, and TNF. Cells were exposed to a bovine serum albumin (BSA) control or either eicosapentaenoic acid (EPA, 20:5n-3) or arachidonic acid (AA, 20:4n-6) in the form of soaps loaded onto BSA for 4 days and wounded on Day 5. AA and EPA improved the healing of an in vitro wound over 72 hr. EPA increased collagen synthesis and the overall percentage of collagen produced, but AA reduced collagen production and total protein. PGE2 production was increased in the AA-treated group and decreased in the EPA-treated group, but was not affected by wounding. IL-1 was not produced at the time point evaluated, but TNF and IL-6 were both produced, and their levels varied relative to the PUFA or wounding treatment. There was a significant linear correlation (r2 = 0.57, P = 0.0045) between IL-6 level and collagen production. These results demonstrate that n-3 PUFA (represented by EPA in this study) positively affect the healing characteristics of MCL cells and therefore may represent a possible noninvasive treatment to improve ligament healing. Additionally, these results show that MCL fibroblasts produce PGE2, IL-6, and TNF and that IL-6 production is related to MCL collagen synthesis.

Dietary conjugated linoleic acids alter serum IGF-I and IGF binding protein concentrations and reduce bone formation in rats fed (n-6) or (n-3) fatty acids.

A study was designed to examine the effects of dietary conjugated linoleic acid (CLA) on serum concentrations of insulin-like growth factor-I (IGF-I) and IGF binding proteins (IGFBP) and the relationship of these factors to bone metabolism. Weanling male rats were fed AIN-93G diet containing 70 g/kg of added fat for 42 days. Treatments included 0 g/kg or 10 g/kg of CLA and soybean oil (SBO) or menhaden oil + safflower oil (MSO) following a 2 x 2 factorial design. Serum IGFBP was influenced by dietary polyunsaturated fatty acid (PUFA) type ((n-6) and (n-3)) and CLA (p = 0.01 for 38-43 kDa bands corresponding to IGFBP-3). CLA increased IGFBP level in rats fed SBO (p = 0.05) but reduced it in those fed MSO (p = 0.01). Rats fed MSO had the highest serum IGFBP-3 level. Both (n-3) fatty acids and CLA lowered ex vivo prostaglandin E2 production in bone organ culture. In tibia, rats given CLA had reduced mineral apposition rate (3.69 vs. 2.79 microm/day) and bone formation rate (BFR) (0.96 vs. 0.65 microm3/microm2/day); however, the BFR tended to be higher with MSO. Dietary lipid treatments did not affect serum intact osteocalcin or bone mineral content. These results showed that dietary PUFA type and CLA modulate local factors that regulate bone metabolism.

Unusual myocardial (myostromal) "repair" in cardiac transplant patient.

A 57-year-old man received a cardiac allograft for severe ischemic heart disease. His endomyocardial biopsy at eight weeks postoperatively showed a focus of unusual myocardial morphology characterized by small diameter myocytes associated with loose, myxoid appearing stroma and a myocytic mitotic figure. We feel this may represent a unique type of myocardial repair.

Dietary lipids modulate bone prostaglandin E2 production, insulin-like growth factor-I concentration and formation rate in chicks.

This study examined the effects of dietary fat on the fatty acid composition of liver and bone, and on the concentration of insulin-like growth factor-I (IGF-I) in liver and bone, as well as the relationship of these factors to bone metabolism. Day-old male broiler chicks were given a semipurified diet containing one of four lipid sources: soybean oil (SBO), butter+corn oil (BC), margarine+corn oil (MAC), or menhaden oil+corn oil (MEC) at 70 g/kg of the diet. At 21 and 42 d of age, chicks fed MEC had the highest concentration of (n-3) fatty acids [20:5(n-3), 22:5(n-3) and 22:6(n-3)] in polar and neutral lipids of cortical bone but the lowest amount of 20:4(n-6) in polar lipids. Diets containing t-18:1 fatty acids (MAC and BC) resulted in t18:1 accumulation in bone and liver. Bone IGF-I concentration increased from 21 to 42 d in chicks given the SBO and BC diets. Tibial periosteal bone formation rate (BFR) was higher in chicks given BC compared with those consuming SBO and MEC at 21 d. The higher BFR and concentrations of hexosamine in serum and IGF-I in cartilage, but lower 20:4(n-6) content in bone polar lipids in chicks given BC compared with those given SBO suggest that BC optimized bone formation by altering the production of bone growth factors. A second study confirmed that dietary butter fat lowered ex vivo prostaglandin E2 production and increased trabecular BFR in chick tibia. These studies showed that dietary fat altered BFR perhaps by controlling the production of local regulatory factors in bone.

Hepatic fatty acid synthase gene transcription is induced by a dietary copper deficiency.

A dietary copper (Cu) deficiency is associated with a twofold increase in hepatic fatty acid biosynthesis. We hypothesized that the induction of hepatic lipogenesis associated with a dietary Cu deficiency reflected an enhanced expression of genes encoding lipogenic enzymes, i.e., fatty acid synthase (FAS). Male weanling rats were pair-meal fed for 42 days a high-sucrose diet that was Cu deficient (CuD; 0.7 microgram Cu/g) or Cu adequate (CuA; 5.0 micrograms Cu/g). The CuD diet increased FAS enzymatic activity twofold (P < 0.05). This rise in enzymatic activity was accompanied by a threefold increase in FAS mRNA and a 2.5-fold increase in FAS gene transcription (P < 0.05). Neither the mRNA abundance nor the rate of gene transcription for phosphoenolpyruvate carboxykinase or beta-actin was affected by the CuD diet. The induction of FAS gene transcription was associated with a 65-85% increase in hepatic reduced glutathione (GSH; P < 0.05). When hepatic GSH synthesis was suppressed by treating CuD rats with L-buthionine sulfoximine, the induction of FAS expression was completely prevented. Similarly, feeding N-acetylcysteine to CuA rats increased hepatic GSH levels 2.5-fold, and this was accompanied by a significant induction in FAS expression. These data indicate that the increase in hepatic lipogenesis associated with a Cu deficiency reflects an induction in hepatic lipogenic gene transcription (i.e., FAS) and that the rate of gene transcription may be dependent on hepatic thiol redox.

Maternal and perinatal long-chain fatty acids: possible roles in preterm birth.

OBJECTIVE: We conducted a case-control study to evaluate whether maternal and fetal omega-3 and omega-6 essential fatty acid status play possible roles in the pathogenesis of preterm birth. STUDY DESIGN: Essential fatty acid status in blood and trophoblast tissues was measured in (1) women and their newborns with spontaneous preterm birth and (2) control women and newborns at 34 weeks' gestation (maternal blood) and at term delivery. RESULTS: Thirty-seven preterm (mean gestational age 34 weeks) and 34 control mother-baby dyads (gestational age 40 weeks) were evaluated. The maternal percent of total arachidonic acid in red blood cells and plasma was increased in preterm cases versus controls at delivery (3.8- and 1.6-fold, respectively, p < 0.05). Maternal red blood cell eicosapentaenoic acid (1.98 +/- 0.15, p < 0.0001) and omega-3/omega-6 ratios (0.58 +/- 0.22, p < 0.009) were lower in preterm cases than in controls at delivery (4.64 +/- 0.32 and 1.27 +/- 0.12, respectively). Docosapentaenoic acid, a marker of omega-3 essential fatty acid deficiency, was higher in preterm maternal red blood cells (1.26 +/- 0.18, p < 0.0001) and amnion (1.27 +/- 0.19, p < 0.001) compared with term controls (0.12 +/- 0.07 and 0.58 +/- 0.13, respectively). CONCLUSION: Women delivered preterm demonstrated higher arachidonic acid and docosapentaneoic acid levels in maternal blood and trophoblast tissue than did women delivered at term. This suggests (1) altered essential fatty acid intake or metabolism in a portion of women delivered preterm and (2) increased maternal red blood cell arachidonic acid is associated with an increased risk of preterm birth.

Prostaglandins in selected reproductive tissues in preterm and full-term gestations.

We investigated differences in maternal plasma and trophoblast prostaglandin metabolism associated with preterm births. Tissue prostaglandins (PGs) E2 and F2 alpha and the stable plasma PGF2 alpha metabolite, 13,14-dihydro-15-keto-PGF2 alpha, were measured in preterm (< 37 weeks) and term (< or = 37 weeks) births. Amnion PGE2 in preterm (106.1 +/- 15.7 ng/g wet weight tissue; x +/- SEM; n = 37) was lower than in term (176.6 +/- 22.7 ng/g wet weight; x +/- SEM; n = 34, P < 0.02). Placenta PGE2 was lower in preterm (34.7 +/- 19.7 ng/g wet weight; x +/- SEM) than in term (103.3 +/- 28.0 ng/g wet weight; x +/- SEM, P < 0.04). Preterm PGF2 alpha was consistently lower in the amnion (106.8 +/- 17.5 ng/g wet weight) and placenta (102.5 +/- 8.7 ng/g wet weight) than in term amnion (188.2 +/- 24.8 ng/g wet weight; P < 0.01) and placenta (128.9 +/- 7.8 ng/g wet weight; P < 0.03). Chorionic PGE2 and plasma PGF2 alpha metabolite followed this trend but did not reach significance. These findings suggest qualitative and quantitative differences in maternal and trophoblast eicosanoid metabolism between term and preterm parturition.

Dietary (n-3) and (n-6) polyunsaturates and acetylsalicylic acid alter ex vivo PGE2 biosynthesis, tissue IGF-I levels, and bone morphometry in chicks.

This study examined the effects of dietary (n-6) and (n-3) polyunsaturated fatty acids (PUFA) and acetylsalicylic acid (ASA) on bone ash content, morphometry, fatty acid composition, ex vivo PGE2 biosynthesis, tissue IGF-I concentration, and serum alkaline phosphatase (ALPase) activity in chicks. Newly hatched chicks were fed a semipurified diet containing soybean oil (S) or menhaden oil / safflower oil (M) at 90 g/kg. At 4 days of age, chicks were divided into four equal treatment groups receiving 0 mg [symbol: see text] or 500 mg [symbol: see text] of ASA/kg of diet: S[symbol: see text]ASA, M[symbol: see text]ASA, S[symbol: see text]ASA, and M[symbol: see text]ASA. Lipid and ASA treatments did not affect bone length, bone ash, or bone mineral content in chicks. Chicks fed M had increased fractional labeled trabecular surface and tissue level bone formation rates, independent of ASA treatment, compared with those given S. A significant fat x ASA interaction effect was found for trabecular bone volume, thickness, separation, and number. Chicks fed S had higher 20:4(n-6) but lower 20:5(n-3) concentrations in liver and bone compared with those given M. Ex vivo PGE2 biosynthesis was higher in liver homogenates and bone organ cultures of chicks fed S compared with the values for those given M at 17 days. ASA treatment decreased ex vivo PGE2 production in liver homogenates and bone organ cultures of chicks, independent of the dietary lipids. Chicks fed ASA had a lower concentration of IGF-I in tibiotarsal bone compared with those not given ASA at 19 days. Serum ALPase activity was higher in chicks given M compared with those fed S, but the values were reversed with ASA feeding. This study demonstrated that both dietary fat and ASA modulated bone PGE2 biosynthesis, and that (n-3) PUFA and fat x ASA interactions altered bone morphometry.

Suppression of renal gamma-glutamylcysteine synthetase expression in dietary copper deficiency.

A dietary deficiency of copper (CuD) is associated with a 50-70% and a 2-fold increase in hepatic reduced glutathione (GSH) concentration and synthesis, respectively, which leads to a 50-80% increase in plasma GSH. Moreover, the kidneys of CuD rats remove 40% more GSH from the blood than copper adequate (CuA) rats. These findings have led us to propose that the increase in hepatic synthesis of GSH in CuD rats is accompanied by a comparable increase in the hepatic expression of gamma-glutamylcysteine synthetase (gamma-GCS), the rate limiting enzyme of glutathione biosynthesis, and that the enhanced uptake of GSH by the kidney would lead to a compensatory decrease in renal gamma-GCS expression. In experiment I, male weanling rats (3-4 weeks) were ad libitum fed a CuD (0.5 microgram Cu/g) or CuA (5.8 micrograms/g) diet for 70 days; and in experiment II, male weanling rats were pair-meal fed the CuD or CuA diet for 35 days. In both studies, CuD diet caused a significant increase in hepatic GSH concentration, but hepatic gamma-GCS activity and mRNA abundance were unchanged. In contrast, renal GSH concentration was unaffected by the CuD diet. However, renal gamma-GCS activity was reduced 40% and this was paralleled by a 50% decrease in gamma-GCS mRNA. Moreover, the decrease in renal gamma-GCS mRNA was caused by a reduction in renal gamma-GCS gene transcription. The results of these studies indicate that the increase in renal uptake of GSH resulting from a dietary Cu deficiency is associated with a compensatory decrease in gamma-GCS expression.

Plasma ascorbic acid concentrations are related to cardiovascular risk factors in African-Americans.

This study was undertaken to examine relationships among blood pressure, blood lipids, and plasma concentrations of ascorbic acid and malondialdehyde (MDA) equivalents (indicative of lipid peroxidation) in adult African-Americans. Subjects (n = 172, mean age = 48.0 y) were recruited from among the memberships of several Seventh-Day Adventist Churches. Plasma ascorbic acid and MDA equivalents were inversely correlated (r = -0.44, P < 0.0001). There were significant inverse correlations between plasma ascorbic acid levels and both systolic (r = -0.39, P < 0.0001) and diastolic blood pressure (r = -0.25, P < 0.03), and between plasma ascorbic acid and serum total cholesterol (r = -0.25, P < 0.03), LDL-cholesterol (LDL-C) (r = -0.33, P < 0.004), and the ratio of LDL-cholesterol to HDL-cholesterol (LDL-C/HDL-C) (r = -0.32, P < 0.004). Serum HDL-cholesterol was positively related to plasma ascorbic acid (r = 0.22, P < 0.05). The correlations for MDA equivalents and the blood pressure and blood lipid variables were of similar magnitude to those of plasma ascorbic acid, but were in the opposite direction. Multiple regression analysis revealed ascorbic acid to be a significant independent contributor to the prediction of blood pressure and LDL-C concentration. These data suggest that plasma concentrations of ascorbic acid and MDA equivalents are related to several cardiovascular risk indicators in black Americans.

Low-dose aspirin does not attenuate platelet aggregation or atherosclerosis in miniature swine but decreases production of aortic wall prostacyclin.

The objectives of this study were to determine if, and at what dose, aspirin could attenuate atherosclerosis in hypercholesterolemic Yucatan miniature swine, and to determine the influence of aspirin on aortic wall prostacyclin production and platelet aggregation. 30 Yucatan miniature swine (age 3 months) were fed either regular diet (RD), atherogenic diet (AD), or AD plus one of four aspirin dosages (2,4,8, or 16 mg/kg/d) for 6 months. The extent of atherosclerotic lesions in the abdominal aorta and coronary arteries was evaluated by sudanophilic staining and histological grading using Stary's classification, respectively. Aortic wall production of prostacyclin (PGI2) and platelet aggregation were assessed. Lesions were similar among the AD groups (45.3 +/- 4.3%) and significantly higher than RD (1.4 +/- 0.4%). PGI2 production was significantly lower (p < 0.05) in all aspirin-treated groups. Platelet aggregation was not affected by treatment. It is concluded that the range of aspirin dosages (2-16 mg/kg/d) does not attenuate the development of atherosclerosis.