No detectable carotenoid concentrations in serum of llamas and alpacas.

Carotenoids are lipid-soluble pigments and important for a variety of physiological functions. They are major dietary vitamin A precursors and act as lipophilic antioxidants in a variety of tissues and are associated with important health benefits in humans and animals. All animals must acquire carotenoids from their diet, but to our knowledge, there are no studies investigating the intestinal carotenoid absorption and their blood concentrations in New World camelids. The present study aimed to assess the serum concentrations of selected carotenoids in llamas (n = 13) and alpacas (n = 27). Serum carotenoids as well as retinol (vitamin A) and α-tocopherol (vitamin E) were determined by high-performance liquid chromatography coupled with mass spectrometry and these were unable to detect any carotenoids (α- and ß-carotene, α- and ß-cryptoxanthin, lutein, zeaxanthin, lycopene) in the samples. The concentrations of retinol in alpacas (2.89 ± 1.13 µmol/l; mean ± SD) were higher (p = 0.024) than those found in llamas (2.05 ± 0.87 µmol/l); however, the concentrations of α-tocopherol were not significantly (p = 0.166) different (llamas: 3.98 ± 1.83 µmol/l; alpacas: 4.95 ± 2.14 µmol/l). The results show that both llamas and alpacas are not able to absorb intact carotenoids, but efficiently convert provitamin A carotenoids to retinol.

Effect of dietary α-tocopherol on the bioavailability of lutein in laying hen.

Lutein and its isomer zeaxanthin have gained considerable interest as possible nutritional ingredient in the prevention of age-related macular degeneration (AMD) in humans. Egg yolk is a rich source of these carotenoids. As an oxidative sensitive component, antioxidants such as α-tocopherol (T) might contribute to an improved accumulation in egg yolk. To test this, chickens were fed lutein esters (LE) with and without α-tocopherol as an antioxidant. After depletion on a wheat-soya bean-based lutein-poor diet for 21 days, laying hens (n = 42) were equally divided into three groups and fed the following diets for 21 days: control (basal diet), a LE group (40 mg LE/kg feed) and LE + T group (40 mg LE plus 100 mg T/kg feed). Eggs and blood were collected periodically. Carotenoids and α-tocopherol in yolk and blood plasma were determined by HPLC. Egg yolk was also analysed for total carotenoids using a one-step spectrophotometric method (iCheck((™)) ). Lutein, zeaxanthin, α-tocopherol and total carotenoids in egg yolk were highest after 14 days of feeding and decreased slightly afterwards. At the end of the trial, eggs of LE + T group contained higher amount of lutein (13.72), zeaxanthin (0.65), α-tocopherol (297.40) and total carotenoids (21.6) compared to the LE group (10.96, 0.55, 205.20 and 18.0 mg/kg, respectively, p < 0.05). Blood plasma values of LE + T group contain higher lutein (1.3), zeaxanthin (0.06) and tocopherol (20.1) compared to LE group (1.02, 0.04 and 14.90 mg/l, respectively, p < 0.05). In conclusion, dietary α-tocopherol enhances bioavailability of lutein reflecting higher content in egg yolk and blood plasma. Improved bioavailability might be due to increased absorption of lutein in the presence of tocopherol and/or a greater stability of lutein/zeaxanthin due to the presence of α-tocopherol as an antioxidant.

Effects of oral supplementation with ß-carotene on concentrations of ß-carotene, vitamin A and α-tocopherol in plasma, colostrum and milk of mares and plasma of their foals and on fertility in mares.

In this study, effects of oral ß-carotene supplementation to mares (ß-carotene group: 1000 mg/day, n = 15; control group: n = 15) from 2 weeks before foaling until 6 weeks thereafter on concentrations of ß-carotene, vitamin A and α-tocopherol in plasma, colostrum and milk and plasma of their foals were determined. In addition, effects on fertility were studied. Beta-carotene concentrations increased in plasma and colostrum of ß-carotene-supplemented mares compared to control mares (p < 0.05). In mares of both groups, ß-carotene concentrations were higher in colostrum than in milk (p < 0.05). In foals, ß-carotene concentrations increased with colostrum uptake and were higher in foals born to supplemented mares (p < 0.05; control group: 0.0003 ± 0.0002 µg/ml on day 0, 0.008 ± 0.0023 µg/ml on day 1; ß-carotene group: 0.0005 ± 0.0003 µg/ml on day 0, 0.048 ± 0.018 µg/ml on day 1). Concentrations of vitamin A and α-tocopherol were higher in colostrum than in milk (p < 0.05) but did not differ between groups. Concentration of α-tocopherol in plasma of mares decreased over time and in foals, increased markedly within 4 days after birth. All but one mare (control group) showed oestrus within 2 weeks post-partum. Occurrence of oestrus did not differ between groups. More mares of the control group (7/7 vs. 5/12 in the ß-carotene group) became pregnant after being bred in first post-partum oestrus (p < 0.05). In conclusion, ß-carotene supplementation to mares increased ß-carotene concentrations in plasma, colostrum and milk of mares and plasma of their foals but had no positive effects on fertility.

Concentrations of retinol, 3,4-didehydroretinol, and retinyl esters in plasma of free-ranging birds of prey.

This study investigated vitamin A compounds in the plasma of healthy free-ranging Central European raptors with different feeding strategies. Plasma samples of nestlings of white-tailed sea eagle [white-tailed sea eagle (WTSE), Haliaeetus albicilla) (n = 32), osprey (Pandion haliaetus) (n = 39), northern goshawk (Accipiter gentilis) (n = 25), common buzzard (Buteo buteo) (n = 31), and honey buzzard (Pernis apivorus) (n = 18) and adults of WTSE (n = 10), osprey (n = 31), and northern goshawk (n = 45) were investigated with reversed-phase-high-performance liquid chromatography (RP-HPLC). In WTSE, northern goshawks and common buzzards retinol were the main plasma component of vitamin A, whilst in ospreys and honey buzzards, 3,4-didehydroretinol predominated. The median of the retinol plasma concentration in the nestlings group ranged from 0.12 to 3.80 µm and in the adult group from 0.15 to 6.13 µm. Median plasma concentrations of 3,4-didehydroretinol in nestlings ranged from 0.06 to 3.55 µm. In adults, northern goshawks had the lowest plasma concentration of 3,4-didehydroretinol followed by WTSE and ospreys. The plasma of all investigated species contained retinyl esters (palmitate, oleate, and stearate). The results show considerable species-specific differences in the vitamin A plasma concentrations that might be caused by different nutrition strategies.

[Micronutrients and their relevance for the eye--function of lutein, zeaxanthin and omega-3 fatty acids]. / Mikronährstoffe und ihre Bedeutung für das Auge--Wirkungsweise von Lutein/Zeaxanthin und Omega-3-Fettsäuren.

Micronutrients play an important role in function and health maintenance for the eye. Especially lutein, zeaxanthin and omega-3 fatty acids perform remarkable functions: lutein together with zeaxanthin forms the macular pigment, these carotenoids filter out the damaging blue light component from the sunlight as well as the ultraviolet light which leads to improved contrast sensitivity and less problems with screen glare. Furthermore, the macular pigment has antioxidant and anti-inflammatory effects. The omega-3 fatty acids also possess anti-inflammatory effects and, when converted into neuroprotectin, they protect against oxidative induced apoptosis in the retina. They are also responsible for the fluidity and supply to the photoreceptor membrane. These properties are important for the prevention and treatment of degenerative eye diseases like age-related macular degeneration. However, older people are often not sufficiently supplied of micronutrients in their diet. Because the supply of nutrients can hardly be achieved by dietary change, the additional intake in the form of food supplements is useful in this age group. Scientific studies have shown the positive effects of supplementation with micronutrients such as lutein/zeaxanthin, vitamin C, vitamin E, zinc and omega-3 fatty acids, docosahexaenoic acid and eicosapentaenoic acid (DHA and EPA). Currently available nutritional products are based in part on the ingredients of the ARED study (Age Related Eye Disease Study). According to more recent studies formulations containing lutein and omega-3 fatty acids in physiologically meaningful doses without additional beta-carotene should be preferred. 10 to 20 mg of lutein and zeaxanthin represent a safe daily dose Regarding to the context above, beta-carotene in high doses plays a minor role to the eye and is especially critical for the health of smokers. This paper summarises the functions of the presented micronutrients in the eye and can assist ophthalmologists in advising their patients.

Effect of ß-carotene supply during close-up dry period on the onset of first postpartum luteal activity in dairy cows.

The aim of this study was to examine the effect of ß-carotene supply during the close-up dry period on the onset of first postpartum luteal activity in dairy cows. Twelve cows were supplied with 2000 mg of ß-carotene (20 g Rovimix(®) ß-Carotene containing 10% ß-carotene; DSM Nutrition Japan K.K., Tokyo, Japan) by oral administration daily from day 21 before expected calving date to parturition. Fourteen cows (control) did not receive ß-carotene supplementation. Blood samples were obtained on days 21, 14 and 7 before expected calving date and on days 1, 7, 14, 21 postpartum. When the plasma progesterone concentration exceeded 1 ng/ml by day 21 postpartum, luteal activity was assumed to have been initiated. The result showed that serum ß-carotene concentrations in the ß-carotene cows were higher than in the control cows during the experimental period (p < 0.01). The number of cows with the onset of luteal activity by day 21 postpartum was 9/12 in the ß-carotene cows and 4/14 in the control cows (p < 0.05). Retinol, certain metabolic parameters and metabolic hormones concentrations did not differ between ß-carotene and control cows. In addition, serum retinol concentration in ß-carotene cows without luteal activity was lower than in ß-carotene cows with luteal activity (p < 0.05), and serum gamma-glutamyl transpeptidase concentration in ß-carotene cows with luteal activity (p < 0.05) and control cows without luteal activity (p < 0.01) was higher than in control cows with luteal activity. In conclusion, ß-carotene supply during the close-up dry period may support the onset of luteal activity during early lactation in dairy cows.

Systemic levels of carotenoids from mangoes and papaya consumed in three forms (juice, fresh and dry slice).

BACKGROUND: Vitamin A deficiency is a public health problem in Cameroon. Data on the bioavailability of carotenoid in fruits currently consumed in Cameroon are scarce. OBJECTIVE: To assess the systemic levels of carotenoids from mangoes and papaya consumed as juice, fresh or dried slices. METHODS: Two groups of seven healthy volunteers (24 and 25 years of age; body mass index: 21 and 22 kg/m(2) respectively for subjects fed mango and papaya), were submitted to three types of meal treatments (juice, fresh and dried fruit). On the experiment day, meals served to fasting subjects during breakfast, included bread, yogurt and one of the three forms of fruit. All the treatments lasted only one day during which blood samples were collected three times; during fasting (T(0)), 4 h (T(4)) and 8 h (T(8)) after the test meal. The carotenoids and retinol contents were analysed by high-performance liquid chromatography method. RESULTS: From the major carotenoids present in papaya and mangoes, lutein, alpha-carotene and beta-carotene were found in considerable amounts. Lycopene and cryptoxanthin that were the major carotenoids in papaya samples appeared in low amounts in the chylomicrons. Significant correlations were observed between these carotenoids (at T(0), T(4) and T(8)). The three forms of consumption contributed to the rise of serum retinol levels. A comparison between the three forms revealed that papaya and mangoes consumed in form of juice or fresh fruit are the best forms because they had higher bioavailability values. CONCLUSION: Association of these different forms of consumptions could lead to a better availability of these fruits throughout the year and therefore efficiently contribute to improve vitamin A status of the population.

Comparison of three spectrophotometric methods for analysis of egg yolk carotenoids.

Carotenoids accumulated in the egg yolk are of importance for two reasons. Firstly they are important pigments influencing customer acceptance and secondly they are essential components with positive health effects either as antioxidants or as precursor of vitamin A. Different analytical methods are available to quantitatively identify carotenoids from egg yolk such as spectrophotometric methods described by AOAC (Association of Official Analytical Chemists) and HPLC (High Performance Liquid Chromatography). Both methods have in common that they are time consuming, need a laboratory environment and well trained technical operators. Recently, a rapid lab-independent spectrophotometric method (iCheck, BioAnalyt GmbH, Germany) has been introduced that claims to be less time consuming and easy to operate. The aim of the current study was therefore to compare the novel method with the two standard methods. Yolks of 80 eggs were analysed as aliquots by the three methods in parallel. While both spectrometric methods are only able measure total carotenoids as total ß-carotene, HPLC enables the determination of individual carotenoids such lutein, zeaxanthin, canthaxanthin, ß-carotene and ß-apocarotenoic ester. In general, total carotenoids levels as obtained by AOAC were in average 27% higher than those obtained by HPLC. Carotenoid values obtained by the reference methods AOAC and HPLC are highly correlated with the iCheck method with r(2) of 0.99 and 0.94 for iCheck vs. AOAC and iCheck vs. HPLC, respectively (both p<0.001). Bland Altman analysis showed that the novel iCheck method is comparable to the reference methods. In conclusion, the novel rapid and portable iCheck method is a valid and effective tool to determine total carotenoid of egg yolk under laboratory-independent conditions with little trained personal.

Effects of basic fibroblast growth factor, transforming growth factor-beta and nerve growth factor on the secretory function of the bovine corpus luteum in vitro.

The effects were investigated of basic fibroblast growth factor (bFGF), transforming growth factor-beta (TGF-beta) and nerve growth factor (NGF) on the release of progesterone and oxytocin from the bovine corpus luteum (CL) at different stages of the oestrous cycle. A microdialysis system (MDS) of CL and a cell culture system with a reduced number of endothelial cells were used. In the MDS of CL from the mid-luteal stage (days 8-12 of the oestrous cycle), infusion with bFGF (0.1, 1, 10 and 100 ng/ml), TGF-beta (0.1, 1 and 10 ng/ml) and NGF (0.1, 1, 10 and 100 ng/ml) for 30 min induced significant acute effects on the release of progesterone. Both bFGF and NGF stimulated the release of progesterone during peptide infusion, TGF-beta and also bFGF in the period thereafter. This stimulation was dose-dependent during and after the infusion only for bFGF. This response pattern was observed at all luteal stages for the three growth factors, but bFGF was more stimulatory at the early (days 5-7) and mid-luteal stages during and after peptide infusion. The release of oxytocin was stimulated by bFGF in a dose-dependent manner. At the highest dose, bFGF, TGF-beta and NGF stimulated the release of oxytocin throughout all three luteal stages. When luteal cells were cultured with growth factors, only TGF-beta showed a dose-dependent inhibition of both basal and LH-stimulated progesterone as well as oxytocin release (measured between 48 and 52 h of culture). NGF had an inhibitory effect only on the basal release of oxytocin. bFGF had no effect on the release of either hormone under continuous stimulation in cell culture. The results indicate that bFGF, TGF-beta and NGF act directly and acutely on the secretory function of bovine CL in the MDS but also have long-term effects as shown in cell culture. bFGF appears to be an important autocrine/paracrine regulator of CL function, since local expression of its mRNA, peptide synthesis and its mitogenic and non-mitogenic actions have now been confirmed. Endothelial cells from the CL have been identified as target cells for bFGF. Differences observed between the two systems might thus be attributed to the presence or absence of cell-to-cell contact and a reduced number of endothelial cells, as well as to the duration of peptide stimulation and medium changes every 24 h compared with the flow-through conditions in the MDS.

Immunolocalization of retinol-binding protein, cellular retinoic acid-binding protein I and retinoid X receptor beta in the porcine reproductive tract during the oestrous cycle.

Retinoid-binding proteins and nuclear receptors are expressed in the reproductive tissues of different species and their expression is hormonally regulated. In the present study, we demonstrated immunocytochemically the temporal and spatial localization of retinol-binding protein (RBP), cellular retinoic acid-binding protein I (CRABPI) and retinoid X receptor beta (RXRbeta) in porcine ovary, oviduct and uterus during the oestrous cycle. RBP and CRABPI were localized in the cytoplasm, whereas RXRbeta occurred in the nucleus. RBP was not detected in either the ovary or the oviduct at any stage of the oestrous cycle. CRABPI was present in luteal cells of the ovary only during dioestrus and in glandular and ciliated cells of the oviduct during oestrus. In the ovary, RXRbeta was always present in granulosa cells and germinal epithelium, with highest levels observed during oestrus. In the uterus, RXRbeta was present throughout the cycle in both the endometrium and the myometrium. However, changes in RXRbeta were observed in the endometrium, with highest levels observed during dioestrus. RBP and CRABPI could be observed in the endometrium only during dioestrus. The results show that the occurrence of retinoid-binding proteins and nuclear receptors in individual tissues of the reproductive tract are strongly dependent on the stage of the oestrous cycle. In the oviduct, the expression of CRABPI seems to be dependent on oestrogen, whereas in the uterus the expression of RBP and CRABPI is influenced by progesterone. The association of expression in different sections of the reproductive tissues investigated shows that the presence of specific proteins involved in retinoid metabolism was dependent on events associated with ovulation, the migration of the oocyte through the oviduct and the possible implantation of the blastocyst into the uterus.

Effects of prostaglandins and oestradiol-17 beta on oxytocin binding in cultured bovine luteal cells.

The aim of the investigation was to evaluate the possible action of prostaglandins (PGs) and oestradiol-17 beta (oestradiol) on the specific binding for oxytocin in bovine luteal cells. Cultured cells of bovine corpora lutea at the mid-luteal stage (Day 8-12 of the oestrous cycle) were examined for the presence of oxytocin receptors by a radioreceptor assay using the 125I-labelled oxytocin antagonist [d(CH2)5,Tyr(Me)2,Thr4,Tyr-NH29]-vasotocin (125I-OVT) as a ligand. The cells were cultured for 48 h in total. In the final 15 h of culture, the luteal cells were exposed to varying concentrations of PGF2 alpha, PGE2 and/or oestradiol. After culture, the cells were incubated with 37,000 dpm (0.5 nM) 125I-OVT with or without 100 nM of unlabelled oxytocin. PGF2 alpha, at 10(-8) M and 10(-7) M, stimulated the specific binding for oxytocin to levels as high as 128% of controls (P < 0.01); by contrast, PGE2, PGI2 or oestradiol had no effect on oxytocin binding. Scatchard analysis revealed that the concentration of oxytocin receptors was increased (P < 0.05) from 6.7 fmol micrograms-1 DNA to 8.4 fmol micrograms-1 DNA by stimulation with 10(-7) M of PGF2 alpha without changing the binding affinity. No further increase in the specific binding was observed when PGF2 alpha was used in combination with PGE2, PGI2 or oestradiol at a concentration of 10(-7) M. Addition of indomethacin (28 microM) resulted in the inhibition of PGF2 alpha secretion, coinciding with a significant decrease in oxytocin binding (P < 0.01). However, addition of arachidonic acid (100 microM) caused a significant increase in the secretion of PGF2 alpha and the specific binding for oxytocin concomitantly (P < 0.05). When the protein kinase C (PKC) activity of the luteal cells was inactivated by preincubating cells for 13 h with 1 microM phorbol 12-myristate 13-acetate before PGF2 alpha stimulation, the specific binding for oxytocin was not affected by PGF2 alpha stimulation (10(-7) M) in the final 15 h of culture. These data suggest that PGF2 alpha may be one of the potent regulators for luteal oxytocin receptors in a paracrine and/or autocrine manner, and that its action is mediated by PKC.

Plasma and tissue concentrations of beta-carotene and vitamin A in rats fed beta-carotene in various fats of plant and animal origin.

We investigated the effects of various types of dietary fat of plant and animal origin on beta-carotene absorption and tissue accumulation in rats. Rats were fed 1 mL of butter fat, lard, tallow, sunflower, arachidonic, soya, olive, or linseed oil containing 175 mg beta-carotene/mL fat by gavage, twice a week for 4 weeks. The beta-carotene and vitamin A levels in plasma and tissues were determined by rp-HPLC. The highest levels of absorbed beta-carotene were observed in the liver of animals fed olive and arachidonic oil (p < 0.001), and in the lungs of animals fed sunflower oil. Histomorphological studies showed that the observed highly variable accumulation of beta-carotene in lung tissue was most probably due to an endogenously caused lipid pneumonia. No beta-carotene was observed in blood plasma, kidney, and spleen in any group. Plasma vitamin A levels (retinol) were increased with tallow, olive, and arachidonic oil (p < 0.05). The most obvious influence was found for vitamin A in the spleen. Levels in rats fed tallow (p < 0.05), butter, or lard (p < 0.001) were higher than in controls. The lowest vitamin A levels were found in rats fed fat of plant origin. Our results suggest that the type of dietary fat can modulate the absorption of beta-carotene as well as the distribution of vitamin A in plasma and selected tissues.

Transfer of fat-soluble vitamins and PCBs from mother to pups in grey seals (Halichoerus grypus).

Lactation in seals is characterized by a rapid and enormous lipid transfer from mother to pups within a milk rich in lipids. Since grey seals do not feed during lactation, all milk constituents are solely derived from body stores. Monitoring levels of fat-soluble vitamins as well as PCBs in blubber and milk may give an insight into the mechanisms involved in their mobilization from blubber, transfer into milk and deposition in the blubber of pups. During lactation, total lipids in milk increased from 261 to 601 g/l. While the level of PCBs in milk per g lipid remained constant throughout lactation, vitamin E, as well as vitamin A and cholesterol, showed a marked decrease during lactation when expressed as quantity per unit lipid. An incomplete transfer of all components from maternal blubber to milk was observed, except for vitamin E. The milk of pregnant females had vitamin E levels per unit which were three times higher than that in blubber, indicating a mobilization of vitamin E from the liver. During the later stages of lactation, there were no differences between the levels of vitamins A and E per unit lipid in the milk and the blubber of suckling pups. The close correlation of PCBs with total milk lipids and the drastic decrease in all other monitored fat-soluble components in seal milk with the progress of lactation point to different mechanisms of mobilization and transport for triglycerides and PCBs compared to fat-soluble vitamins and cholesterol.

Carotene cleavage activity in bovine ovarian follicles.

Carotene cleavage activity has been demonstrated in bovine ovarian follicles by incubating cell-free homogenates from granulosa cells with 15, 15'-(14)C-beta-carotene. Enzyme activity was highly dependent on the quality of follicles studied. Highest cleavage activity was found in large, preovulatory follicles. The correlation between follicular fluid concentration of vitamin A and the conversion rate obtained with the corresponding enzyme preparations was significantly positive. No correlation, however, could be shown between cleavage activity and beta-carotene, alpha-tocopherol or cholesterol. The only form of vitamin A in follicular fluid of cattle was found to be retinol. The results support the hypothesis that a local conversion of beta-carotene into vitamin A in follicular structures is responsible for the increase of the intrafollicular concentration of vitamin A during follicular development.

Effect of parturition on levels of vitamins A and E and of beta-carotene in plasma and milk of mares.

The objective of this study was to investigate in mares the effect of parturition on plasma and milk levels of retinol, beta-carotene, alpha-tocopherol and cholesterol over 12 weeks around parturition. In blood plasma of horses around parturition an increase of all these components was observed. This increase was most impressive in beta-carotene (P<0.05) and less pronounced for vitamin E, vitamin A and cholesterol. The magnitude of increase around parturition corresponded well with the magnitude of accumulation in colostrum; levels of beta-carotene in colostrum were 65 times higher compared to mature milk while vitamin A, vitamin E and cholesterol were only 3 to 8 times higher. Beta-carotene concentrations in colostrum were positively correlated with corresponding plasma levels (r = 0.9; P<0.001). Reasons for the increase in plasma beta-carotene around parturition may include an improved absorption of carotene and/or reduced conversion into vitamin A as well as mobilisation from tissue storages or a reduced uptake in tissues other than the mammary gland. In conclusion, the results may point to possible component- and species-specific differences involved in the transfer of fat-soluble vitamins, beta-carotene and cholesterol from blood plasma into colostrum.

Insensitivity of dogs to the effects of nonspecific bound vitamin A in plasma.

Retinol bound to its specific carrier, the retinol-binding protein, is known to be the physiological way vitamin A is transported in blood. Unspecific, lipoprotein-bound vitamin A has so far only be reported under the condition of hypervitaminosis A. In this investigation vitamin A concentrations in dog plasma are reported (2300 ng/ml), showing for the first time a species which, under physiological conditions, transports most of its vitamin A in plasma as retinyl esters (70%) associated with lipoproteins. This phenomenon might indicate that dogs are less sensitive to the effects of nonspecific delivery of vitamin A than other species. This can open new aspects in retinoid research, especially with regard to hypervitaminosis A - an undesirable side effect of the beneficial use of retinoids in dermatology and oncology.

Vitamin A in blood plasma and urine of dogs is affected by the dietary level of vitamin A.

Dogs differ from other species with respect to the occurrence of a high percentage of retinyl esters in blood plasma and the excretion of substantial amounts of vitamin A in the urine. Our investigation focussed on the effects of different concentrations of vitamin A in the diet, ranging from concentrations below NRC requirements of 25 IU/kg body weight (BW) to 2400 IU/kg BW, on the levels of retinol and retinyl esters (palmitate/oleate and stearate) in canine blood plasma and urine. The plasma levels of retinyl esters paralleled the levels of vitamin A in the feed (r = 0.91; p < 0.001). The highest plasma level (12.1 +/- 0.4 mg/l) was observed at the highest level in the diet. This observation may be explained by the fact that in dogs retinyl esters are associated with lipoproteins. Even under prolonged feeding on vitamin A levels below NRC requirements, retinyl esters were still present in the plasma (2.8 +/- 0.1 mg/l). Levels of retinol were not affected (1.2 +/- 0.03 vs. 1.0 +/- 0.03 mg/l, respectively). In the urine, the concentration of retinol and retinyl palmitate/oleate increased with the first increase of vitamin A in the diet to 1.2 +/- 0.4 mg/l of total vitamin A. Urinary levels were elevated and fluctuated with up to four peaks while dietary vitamin A levels were above NRC requirements. But the amount of retinol and retinyl esters excreted did not show any dependence on the amount of vitamin A in the diet. When the amount of vitamin A in the diet was at or below requirements, only traces of retinol and retinyl esters were detected in urine. Thus, contrary to current knowledge for most other mammals, retinyl ester levels in plasma and retinol and retinyl esters in the urine of dogs proved to be clearly but differently affected by the amount of vitamin A supplied with the diet. Contrary to retinol, plasma levels of retinyl esters closely reflect the actual supply of vitamin A with the feed. The occurrence of retinol and retinyl esters in urine may, however, be due to dietary supply of vitamin A in excess of standard requirements, thereby providing a useful indicator of a dietary supply of vitamin A above requirement. The mechanism involved in the possible regulation of urinary excretion of retinol and retinyl esters remains to be elucidated.

Vitamin A status in the grey seal (Halichoerus grypus) on Sable Island.

Vitamin A and beta-carotene concentrations in serum, liver and blubber fat were investigated in 65 grey seals of different age and sex in the pupping colony on Sable Island, Canada to determine the vitamin A status. In none of the investigated samples could beta-carotene be detected. There were no differences in the concentration of vitamin A in serum, liver and blubber between male (213 micrograms/l, 376 micrograms/g, 22 micrograms/g respectively) and female (205 micrograms/l, 319 micrograms/g, 19 micrograms/g respectively) juveniles. In adult males concentrations of vitamin A in serum, liver and blubber were higher (260 micrograms/l, 503 micrograms/g, 34 micrograms/g respectively) than in juveniles indicating an age dependent increase of vitamin A in liver and blubber. Contrary to this in lactating females concentrations of vitamin A in serum, liver and blubber were significantly different than in the other animals. While the level of vitamin A in serum and blubber was two times higher with 413 micrograms/1 and 62 micrograms/g respectively, the concentration of vitamin A in liver was much lower (265 micrograms/g) compared to juveniles and adult males. It is possible that the intensified lipid metabolism during lactation, necessary to match the energy requirements of the rapidly growing pup, causes these extreme differences in vitamin A concentrations in serum, liver and blubber of lactating females compared to juveniles and adult males. Due to high concentration of vitamin A in blubber and the high proportion in blubber to total body weight, the blubber represents approximately 40% of total body reserves of vitamin A.

Vitamin A in the urine of carnivores.

Vitamin A levels (retinol equivalents) in the urine of canines were between 423 ng/ml (dog) and 6304 ng/ml (silver fox). Neither vitamin A nor vitamin E was found in the urine of herbivores, omnivorous and rodents. No vitamin A but low levels of vitamin E were detected in cats. Vitamin A in the urine was present as retinol and retinyl esters (basically retinyl palmitate/oleate). The total excretion of vitamin A represented 15 to 63% of the daily uptake in dogs, while less than 4% of vitamin E was excreted. Results after precipitation and ultracentrifugation indicate that similar carrier proteins may exist for retinol, retinyl esters and alpha-tocopherol in the urine. The biological significance of this phenomenon is discussed with regard to the high concentrations of retinyl esters in the blood plasma of carnivores bound to lipoproteins.

Improved extraction procedure for carotenoids from human milk.

An improved method for the extraction of the major carotenoids from human milk is described. Carotenoids were extracted from milk first with ethanol and n-hexane. Then, polar xanthophylls were extracted from n-hexane into ethanol/water. The remaining n-hexane was evaporated, the residue combined with the ethanolic milk fraction and the mixture briefly saponified. Carotenoids were extracted from the hydrolysate with n-hexane, combined with the polar xanthophylls from the non-saponified ethanol/water-extract and separated by HPLC. Using this method we were able to significantly improve the recovery of xanthophylls such as lutein and zeaxanthin from human milk. The recovery rate of all carotenoids was > 90%. This method might not only be of value for milk but should be especially useful in the extraction of carotenoids from human tissues such as the adipose tissue.