STRUCTURAL CHANGES IN ISOLATED LIVER MITOCHONDRIA OF RATS DURING ESSENTIAL FATTY ACID DEFICIENCY

Liver mitochondria isolated in 0.44 M sucrose from rats deficient in essential fatty acids (EFA) oxidized citrate, succinate, α-ketoglutarate, glutamate, and pyruvate at a faster rate than did mitochondria isolated from normal rats; however, the oxidation of malate, caprylate, and β-hydroxybutyrate was not significantly increased. The mitochondria from deficient rats exhibited an increased ATPase activity and extensive structural damage as revealed by electron microscope examination of thin sections. An increase in citrate oxidation and ATPase activity, together with some structural damage, could be demonstrated as early as the 4^th week in rats on a fat-free diet. Saturated fat in the diet did not prevent the change in mitochondrial structure but accelerated its appearance. Both the biochemical and structural defects could be reversed within three weeks after feeding deficient rats a source of EFA. In the presence of a phosphate acceptor the effect of EFA deficiency on substrate oxidation was largely eliminated. A trend toward a reduced efficiency of oxidative phosphorylation was noted in mitochondria from EFA-deficient rats, but significant uncoupling was found only in the case of citrate, β-hydroxybutyrate, and glutamate in the presence of malonate. Together with the increased ATPase activity, the uncoupling of phosphorylation could account for the poor respiratory control found with the deficient preparation. However, EFA deficiency was without effect on the respiration of liver slices, which supports the belief that the observed changes in oxidation and phosphorylation are an artifact resulting from damage sustained by the deficient mitochondria during their isolation.     

BRAIN RECOVERY FROM ESSENTIAL FATTY ACID DEFICIENCY IN DEVELOPING RATS 1

Abstract— Rats were supplied from before birth with an essential fatty acid (EFA) deficient, a control, or an EFA deficient-control combination diet for various periods up to 6 months. It was found that EFA deficiency resulted in brain weights decreased in comparison with control values throughout development. The brain weight/body weight relationship, however, expressed by Donaldson's equation was generally maintained in animals fed either totally deficient or control diets. Animals deficient even during the brain's most actively growing period were able to recover completely on restoration of the control diet for a sufficiently long period. Fatty acid alterations in brain ethanolamine phosphoglyceride (EPG) during EFA deficiency were extensive. Acids of the ω6 family (18:2, 20:2, 20:3, 20:4, 22:3, 22:4 but not 22:5) were reduced from control figures. In the w9 family 20:3 and 22:3 were especially elevated whereas 22:6 ω3 levels were similar to those of the controls, finally decreasing only after a lengthy period of EFA deprivation. Mean unsaturation contents, as expressed by the proposed unsaturation index notation (Ul_mol) agreed closely in EPG fatty acids of deficient and control rats at a particular age. On substitution of the control for the deficient diet the ω6 family rebounded in a manner such that values for 20:4, 22:4, and 22:5 exceeded comparable figures in control animals. Concomitantly the ω9 family receded below control levels, and ω3 acids remained or returned to normal. This overadjustment in ω6 and ω9 families continued even after a prolonged period on the control diet.     

Effect of maternal fatty acid deficiency on lipid content and composition of rat liver during prenatal development

Two groups of female rats were fed a diet with high (5.9 cal % of linoleate + linolenate) or low (0.78 cal % of linoleate + linolenate) essential fatty acid (EFA) concentration. The effects of the EFA concentration during gestation on liver lipid and fatty acid composition were studied in the fetuses at 15 and 20 days of intrauterine life. Fetal and liver weights were identical in the two groups; at day 20 the contents of proteins, total cholesterol, phospholipids and glycolipids were significantly decreased (p less than 0.01) with the low EFA diet while at day 15 only total cholesterol was affected (p less than 0.05). At both gestational ages the triacylglycerol content was increased in the low EFA group (day 15 p less than 0.05, day 20 p less than 0.01). The maternal EFA deficiency resulted in higher levels of 16:1 n-7 in the phospholipid fractions and 16:1 n-7 and 18:1 n-7 in the neutral lipids. The increase in these monoenoic derivatives partially compensated the decrease of the polyunsaturated species 18:2 n-6 and 20:4 n-6. In conclusion the low EFA diet results in important modifications of the fetal hepatic lipids during intrauterine development.     

Time dependent study to evaluate the efficacy of zinc on hepatic marker enzymes and elemental profile in serum and liver of protein deficient rats

This study was designed to determine the time dependent protective effects of zinc sulfate on the serum and liver marker enzymes along with elemental profile in protein deficient Sprauge Dawley (S.D.) female rats. Zinc sulfate in the dose of 227 mg/l in drinking water was administrated to normal control as well as protein deficient rats for a total duration of 8 weeks. The effects of different treatments were studied on enzymes like alkaline phosphatase (ALP), aspartate aminotransferases (AST) and alanine aminotransferases (ALT) in rat serum at different time intervals of 1, 2, 4 and 8 weeks and in the rat liver at the end of study. The status of different essential elements in liver was also studied. The serum ALP activity got significantly depressed when estimated at the intervals of 4 and 8 weeks. Activity of serum ALT was significantly increased after 4 weeks interval in protein deficient rats and the increasing trend continued upto 8 weeks of protein deficiency. On the other hand, activity of AST showed a significant increase just after 2 weeks and activity continued to be increased up to 8 weeks. Moreover activities of all the hepato marker enzymes showed a significant increase in liver of protein deficient rats. Interestingly, supplementation of Zn to protein deficient rats helped in regulating the altered activities of ALP, AST and ALT both in serum and liver. However, zinc treatment alone to normal rats did not indicate any significant change in the activities of all the enzymes in liver as well serum except at the interval of 2 weeks where a marginal increase in the activity of AST was seen. It has also been observed that concentrations of zinc, copper, iron and selenium were found to be decreased significantly in protein deficient animals. However, the levels of these elements came back to within normal limits when zinc was administrated to protein deficient rats. Published online December 2004     

Effects of infusion of some prostaglandins in essential fatty acid-deficient and normal rats

Infusion of 1 mg/kg per day of prostaglandin E(1) (PGE(1)) for 2 and 7 wk failed to correct the dermal signs of essential fatty acid (EFA) deficiency in rats despite the known conversion of EFA to certain prostaglandins. PGE(1) caused no significant changes in serum cholesterol, triglycerides, or phospholipids or in liver neutral lipids in EFA-deficient or normal rats. In normal rats epinephrine-induced lipolysis was greater in fat pads from infused than from untreated rats. The effect on epinephrine-induced lipolysis was greater after the 7 wk infusion than after the 2 wk infusion. The 7 wk infusion also lowered plasma free fatty acid (FFA) concentrations. Infusion of PGE(2) and PGF(2alpha) in combination for 4 wk had no significant effect on either dermal signs of EFA deficiency, lipolysis, or plasma FFA concentrations.     

Effect of vitamin A deficiency on the pulmonary and hepatic drug-metabolizing enzymes in rat

The effect of vitamin A deficiency on the drug-metabolizing enzyme system of the lung and liver was analyzed in rats fed diets with or without vitamin A for 5-6 weeks. The hepatic level of vitamin A was significantly reduced in vitamin A deficient animals. The hepatic cytochrome P-450 and b5 contents and activity of benzo(a)pyrene hydroxylase was significantly reduced in deficient animals. Contrary to this, pulmonary cytochrome P-450 and b5 contents were above the control values. No alteration in pulmonary benzo(a)pyrene hydroxylase was noted. The uridine diphosphate-glucuronosyltransferase activity of digitonin-treated microsomal membranes was below the control values both in lung and liver. However, the native uridine diphosphate-glucuronosyltransferase activity remained unchanged in the liver and was below control values in the lung.     

Effect of essential fatty acid deficiency on G-proteins, cAMP-dependent protein kinase activity and mucin secretion in the rat submandibular salivary glands

Studies were conducted to determine whether β-adrenergic cell signalling is altered in submandibular salivary glands (SMSG) is essential fatty acid (EFA) deficiency. Three groups of rats were fed diets which were deficient in EFA (EFAD), marginally deficient in EFA (MEFAD) or contained sufficient amount of EFA (Control). Rats were killed after 20 wk on diets, SMSG were dissected out and cyclic AMP-dependent protein kinase (PKA) activity was measured. The specific enzyme activities were higher in the homogenates and supernatant fractions of the gland from EFAD and MEFAD rats compared with the controls. The relative levels of guanine nucleotide-binding regulatory proteins (Gs and Gi) were also measured in the SMSG membranes of rats fed the 3 diets. The levels of Gs were significantly higher in the EFAD and MEFAD groups than in the controls. No significant differences were observed in the secretion of trichloroacetic acid-phosphotungstic acid (TCA-PTA) precipitable glycoproteins from the SMSG slices among the 3 dietary groups.     

Determination of phase I metabolic enzyme activities in liver microsomes of Mrp2 deficient TR- and EHBR rats

The canalicular multispecific organic anion transporter/multidrug resistance protein 2 (cMOAT/Mrp2) plays a major role in the transport of anionic xenobiotics across the bile canalicular membrane. Transport deficient rats (TR-) and Eisai-hyperbilirubinemic rats (EHBR), defective in Mrp2, are mutants of Wistar and Sprague Dawley (SD) rats, respectively. In this study, Phase I metabolic enzyme activities in liver microsomes prepared from these mutant male and female rats were compared to their corresponding non-mutant rats. The total cytochrome P450 contents and NADPH-cytochrome P450 reductase activity in male and female TR- rats were significantly higher than in Wistar rats. In male TR- rats, ethoxyresorufin O-deethylation (EROD), pentoxyresorufin O-deethylation (PROD), testosterone 2alpha, 7alpha and 16 alpha-hydroxylase activities were higher, but testosterone 6beta-hydroxylase activity and the rate of androstenedione formation were lower than in Wistar rats. Female TR- rats had higher 7alpha-hydroxylase activity, but EROD activity was lower in female Wistar rats. Similar studies conducted in EHBR versus SD rats demonstrated increased total cytochrome P450 content in male and female EHBR rats; NADPH-cytochrome P450 reductase activity was not significantly affected. Decreased PROD activity and the rate of androstenedione formation were observed in male and female EHBR rats. Furthermore, testosterone 6beta-hydroxylase activity was lower in male EHBR rats than in male SD rats while testosterone 7alpha-hydroxylase activity was significantly higher in male and female EHBR rats. Thus, in addition to Mrp2 deficiency, differential expression of CYP isoforms and their potential impact on the metabolism and pharmacokinetics of compounds should be considered when interpreting data from these rat strains.     

Regulation of aspartate aminotransferase activity associated with change of pyridoxal phosphate level.

The activities of aspartate aminotransferase (EC 2.6.1.1) in the cytosol fractions of the liver and kidney of rats fed pyridoxine-deficient or control diet for 3 weeks were determined. In the absence of pyridoxal phosphate, the activities in the liver and kidney preparations of deficient rats were both abnormally low. The activity in the kidney fraction of deficient rats was restored to almost the control level by addition of pyridoxal phosphate, whereas that of the liver was only partially restored. The antigen activity, however, measured using anti-aspartate aminotransferase, was similar in liver fractions from deficient and control rats. These findings suggest the existence of a form of transaminase with little or no activity in the liver of deficient rats. The properties of the crude enzymes from deficient and control rats were indistinguishable by immunodiffusion, and the enzymes had the same subunit size and heat stability under the conditions tested. However, purified enzyme from deficient rat liver had a different specific activity and absorption spectrum from purified enzyme from normal liver.     

Purification, composition, and some properties of rat liver carbamyl phosphate synthetase (ammonia).

Hepatic microsomes prepared from vitamin E deficient and supplemented rats were analyzed for cytochrome P-450 content and drug metabolizing activity. Reduced levels of benzo[α]pyrene hydroxylase and ethylmorphine N-demethylase activities were observed in microsomes derived from rats fed a diet deficient in vitamin E compared to those of control rats. NADPH-mediated destruction of P-450, and pentobarbital and zoxazolamine sleeping times were similar in the two groups. Induction with 3-methylcholanthrene raised the levels of benzo[α]pyrene hydroxylase activity of both supplemented and deficient rats to the same absolute levels. No differences were noted in cytochrome P-450 or P-448 content between control and tocopherol deficient rats, nor did the activity of liver catalase differ between the two dietary groups. Thus, these studies did not demonstrate any impairment of heme protein synthesis in vitamin E deficient rats.     

Non-shivering thermogenesis and brown adipose tissue activity in essential fatty acid deficient rats.

The effects of essential fatty acid (EFA) deficiency on energetic metabolism and interscapular brown adipose tissue (BAT) activity were examined in the cold acclimated rat. Weanling male Long-Evans rats were fed on a low fat semipurified diet (control diet, 2% sunflower oil; EFA deficient diet, 2% hydrogenated coconut oil) for 9 weeks. They were exposed at 5 degrees C for the last 5 weeks. In EFA deficient rats, compared to controls, growth retardation reached 22% at sacrifice. Caloric intake being the same in the two groups, it follows that food efficiency was decreased by 40%. Resting metabolism in relation to body surface area was 25% increased. Calorigenic effect of norepinephrine (NE) in vivo (test of non-shivering thermogenesis) underwent a marked decrease of 34%. BAT weight was 21% decreased but total and mitochondrial protein content showed no variation. A 26% increase in purine nucleotide binding per BAT (taken as an index of thermogenic activity) was observed, suggesting that the enhancement in resting metabolism observed was mainly due to increased BAT thermogenesis. However, BAT mitochondria respiratory studies which are more direct functional tests showed a marked impairment of maximal O2 consumption of about 30% with palmitoyl-carnitine or acetyl-carnitine (both in presence of malate) or with alpha-glycerophosphate as substrate. It is likely that this impaired maximal BAT oxidative capacity may explain the impaired NE calorigenic effect in vivo. A possible increase in mitochondrial basal permeability is also discussed.     

Effect of insulin-mimetic vanadyl sulfate on cytochrome P450 2E1-dependent p-nitrophenol hydroxylation in the liver microsomes of streptozotocin-induced type 1 diabetic rats

CYP2E1 is known to be induced in streptozotocin (STZ)-treated diabetic rats (STZ rats), and its induction is improved by insulin. We have examined the age-dependent changes of CYP2E1 in the liver microsomes of type 1 diabetic STZ rats, the effects of VOSO4 on the contents of total P450 and CYP2E1, and the activities of CYP2E1 in terms of p-nitrophenol hydroxylation. The contents of P450 and CYP2E1 and CYP2E1 activity were enhanced with the development of diabetes. When the hyperglycemia of STZ rats was improved by daily intraperitoneal injections of VOSO4 for 10 days at the doses of 7 mg/kg body weight for 5 days, 5 mg/kg for the following 3 days, and then 2.5 mg/kg for 2 days, the P450 and CYP2E1 levels and CYP2E1 activity were lowered than those in the untreated STZ rats. To understand the mechanism underlying CYP2E1-dependent hydroxylation activity, the production of reactive oxygen species was examined in the NADPH-liver microsomal systems by ESR spin-trapping. Singlet oxygen (1O2) was detected in all microsomal systems, while superoxide anion radical(*O2-) and hydroxyl radical (*OH) were not. On the basis of these results, we conclude that (1) CYP2E1 level and activity are enhanced in the diabetic state, however, they are improved by VOSO4 treatment, and (2) 1O2 is generated during CYP2E1-dependent substrate oxygenation.     

BRAIN LIPID MODIFICATIONS INDUCED BY ESSENTIAL FATTY ACID DEFICIENCY IN GROWING MALE AND FEMALE RATS

—Essential fatty acid (EFA) deficiency initiated in rats prior to birth and continued for one year affects brain lipids to an extent which differs in the two sexes. It was found that: (1) Brain weight and lipid content were decreased in deficient conditions, especially in males. (2) Total phospholipids were present in lower concentrations, particularly in the deficient male brain, while the percentage of the major phospholipid classes-ethanolamine phosphoglyceride (EPG), choline phosphoglyceride (CPG) and serine phosphoglyceride (SPG) did not change. (3) Brain EPG, CPG and SPG had distinctive fatty acid patterns differing greatly in polyunsaturation content. PE acids of control females had elevated monoenes and reduced saturates in comparison with control males. This sex difference was lost in the deficient animals. (4) Polyunsaturated fatty acids of EPG, CPG and SPG were markedly changed in animals lacking dietary linoleic acid. Trienoic (C₂₀ and C₂₂) and docosapentaenoic acids were greatly increased, whereas arachidonic, docosatetraenoic and docosahexaenoic acids were much decreased. (5) In spite of the changes in fatty acid composition each of the three phospholipid classes maintained its particular level of unsaturation during EFA deficiency. (6) EPG aldehydes did not change appreciably in deficient conditions.     

Effect of intratracheally instilled benzo(a)pyrene on the pulmonary and hepatic drug-metabolizing enzymes in normal and vitamin A deficient rats

The effect of intratracheal instillation of different doses of benzo(a)pyrene (0.1, 1.0 and 2.0 mg) on the drug metabolizing enzymes of lung and liver was analysed in rats fed diet with or without vitamin A for 5-6 weeks. Benzo(a)pyrene exposure at 2.0 mg dose only elevated the level of cytochrome P-450 and b5, and activity of benzopyrene hydroxylase in liver, and extent of increase was similar in normal and vitamin A deficient groups. Contrary to this, pulmonary contents of cytochrome P-450 and b5, and benzopyrene hydroxylase activity increased over control values in both the groups even at lower doses of benzo(a)pyrene. Moreover, their values were higher in vitamin A deficient-treated groups compared to normal-treated controls. Increase in these parameters was greater in lung as compared to increase in liver. NADPH cytochrome C-reductase in lung and liver was not affected either by inducing vitamin A deficiency or exposing these rats further to benzo(a)pyrene. Uridine-diphospho-glucuronosyl-transferase (UDP-GT) activity in normal and vitamin A deficient groups was enhanced following exposure to benzo(a)pyrene both in lung and liver. However, activity of this enzyme remained impaired in vitamin A deficient groups, benzo(a)pyrene exposed or not exposed when compared to respective normal controls. Glutathione S-transferase activity remained unchanged following exposure to benzo(a)pyrene both in lung and liver. The apparent increase in hepatic glutathione S-transferase and decrease in pulmonary glutathione S-transferase activity in vitamin A deficiency was only due to vitamin A deficient status of rats with no further effect of benzo(a)pyrene.     

Fatty acid composition, eicosanoid production and permeability in skin tissues of rainbow trout (Oncorhynchus mykiss) fed a control or an essential fatty acid deficient diet

Rainbow trout (Oncorhynchus mykiss) were fed either a control diet containing fish oil or an essential fatty acid (EFA) deficient diet containing only hydrogenated coconut oil and palmitic acid as lipid source (93.4% saturated fatty acids) for 14 weeks and the fatty acid compositions of individual phospholipid classes from skin and opercular membrane (OM) determined. The permeability of skin and OM to water and the production of eicosanoids in skin and gills challenged with the Ca²⁺ ionophore A23187 were also measured. Phospholipid (PL) fatty acid compositions were substantially modified in EFA-deficient fish, with increased saturated fatty acids and decreased polyunsaturated fatty acids (PUFA), especially arachidonic acid (AA) and eicosapentaenoic acid (EPA), while docosahexaenoic acid (DHA) was largely retained. The onset of EFA deficiency was shown by the appearance of n-9 PUFA, particularly 20:3n-9. The main effects of EFA deficiency on phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were to increase saturated fatty acids and monoenes, especially 16:1 and 18:1, and to decrease EPA and DHA. The content of DHA in phosphatidylserine (PS) was high in control animals (40% in skin and 35% in opercular membrane) and was mostly retained in EFA deficient animals. Arachidonic acid (AA) was the most abundant PUFA esterified to phosphatidylinositol (PI) and was significantly reduced in EFA deficient animals (from 31% to 13% in skin), where a large amount of 20:3n-9 (9% in skin) was also present. Influxes and effluxes of water through skin and opercular membrane were measured in vitro. No differences were detected between rainbow trout fed the control or the EFA deficient diet. 12-Hydroxyeicosatetraenoic acid (12-HETE), 12-hydroxyeicosapentaenoic acid (12-HEPE) and 14-hydroxydocosahexaenoic acid (14-HDHE) could not be detected in skin from control or EFA deficient fish. There was no difference between control and EFA deficient trout in the levels of leukotriene C₄ (LTC₄) and leukotriene C₅ (LTC₅) in skin cells challenged with the calcium ionophore A23187, and of prostaglandin F_2α (PGF_2α), 12-HETE and 12-HEPE in gill cells challenged similarly. Prostaglandin F_3α (PGF_3α) production by ionophore stimulated gill cells was significantly reduced in fish fed the EFA-deficient diet. 14-HDHE produced by gill cells was 3.3 fold higher in EFA deficient fish compared to controls.     

The effects of in vitro lipid peroxidation on the activity of rat liver microsomal glutathione S-transferase from rats supplemented or deficient in antioxidants

Glutathione S-transferases are a group of multifunctional isozymes that play a central role in the detoxification of hydrophobic xenobiotics with electrophilic centers (1). In this study we investigated the effects of in vitro lipid peroxidation on the activity of liver microsomal glutathione S-transferases from rats either supplemented or deficient in both vitamin E and selenium. Increased formation of malondialdehyde (MDA), a by-product of lipid peroxidation, was associated with a decreased activity of rat liver microsomal glutathione S-transferase. The inhibition of glutathione S-transferase occurred rapidly in microsomes from rats fed a diet deficient in both vitamin E and selenium (the B diet) but was delayed for 15 minutes in microsomes from rats fed the same diet but supplemented with these micro-nutrients (B+E+Se diet). Lipid peroxidation inhibits microsomal glutathione S-transferase and this inhibition is modulated by dietary antioxidants.     

Cytochrome P450 2E1 dependent catalytic activity and lipid peroxidation in rat blood lymphocytes

To investigate the similarities in the catalytic activity of blood lymphocyte P450 2E1 in blood lymphocyte with the liver isoenzyme, NADPH dependent lipid peroxidation and activity of N-nitrosodimethyamine demethylase (NDMA-d) was studied in rat blood lymphocytes. Blood lymphocytes were found to catalyse NADPH dependent (basal) lipid peroxidation and demethylation of N-nitrosodimethylamine (NDMA). Pretreatment with ethanol or pyrazole or acetone resulted in significant increase in the NADPH dependent lipid peroxidation and the activity of NDMA-d in blood lymphocytes and liver microsomes. In vitro addition of CCl(4) to the blood lymphocytes isolated from control or ethanol pretreated rats resulted in an increase in the NADPH dependent lipid peroxidation. Significant inhibition of the basal and CCl(4) supported NADPH dependent lipid peroxidation and NDMA-d activity in blood lymphocytes isolated from control or ethanol pretreated rats by dimethyl formamide or dimethyl sulfoxide or hexane, solvents known to inhibit P450 2E1 catalysed reactions in liver and anti- P450 2E1, have indicated the role of P450 2E1 in the NADPH dependent lipid peroxidation in rat blood lymphocytes. The data indicating similarities in the NADPH dependent lipid peroxidation and NDMA-d activity in blood lymphocyte with the liver microsome have provided evidence that blood lymphocyte P450 2E1 could be used as a surrogate to monitor and predict hepatic levels of the enzyme.     

Sexually Dimorphic Activation of Liver and Brain Phosphatidylethanolamine N-Methyltransferase by Dietary Choline Deficiency

Phosphatidylethanolamine N-methyltransferase (PEMT) activity was measured by a radioenzymatic assay in homogenates of brain and liver obtained from Sprague Dawley rats fed a choline-free or control (0.3 g/kg of choline chloride) diet for seven days. Choline deficiency increased PEMT activity in the liver of male rats by 34% but had no effect on hepatic PEMT in females. In contrast, brain PEMT activity was increased in brain of choline deficient females (by 49%) but was unaltered in males. Activation of the PE methylation pathway in female brain may constitute a compensatory mechanism to sustain PC synthesis during choline deficiency.     

Effects of low-zinc status and essential fatty acid deficiency on bone development and mineralization

1. The effects of essential fatty acids (EFAs) and zinc on the development and mineralization of bones were studied in young growing rats. 2. Female weaning rats were maintained on the diets deficient in EFAs, low in zinc (6 ppm) or both deficient in EFAs and low in zinc. 3. The low-zinc status accentuated signs of EFA deficiency including reduction of the growth rate and weights of bones and resulted in greater incidences of dental caries. 4. There were qualitative and quantitative differences in the fatty acid components of lipids extracted from the femur of the rats. 5. The overall effect was that eicosatrienoic (C20:3) and arachidonic (C20:4) acids were accumulated in EFA deficiency and low-zinc state respectively. 6. Bones of rats fed a low-zinc diet containing no EFAs were totally hypomineralized while those maintained on a diet that was either low in zinc or deficient in EFAs was partially hypomineralized. 7. Dietary zinc may have some roles to play in the biosynthesis of prostaglandins from EFAs and the process of bone mineralization.