No abstract

We investigated the plasma concentration and urinary excretion of vitamin C in cows supplemented with vitamin C. Five cows (mean BW = 597 kg) were allocated to a 5 x 5 Latin square design and supplemented with a vitamin C preparation coated with hydrogenated soybean oil at 0, 10, 20, 40, or 60 mg of vitamin C per kg of BW per day for 9 d. Plasma and urine samples were collected for measuring vitamin C concentration. Urinary excretion of vitamin C was expressed as the ratio of vitamin C to creatinine. Plasma vitamin C concentration and urinary vitamin C excretion increased quadratically as dietary vitamin C increased (P < 0.001); that is, the lowest dose affected neither plasma vitamin C concentration nor urinary vitamin C excretion but the plasma vitamin C concentration and urinary vitamin C excretion increased (P < 0.05) with increasing supplementation of vitamin C at greater doses. This suggests that plasma vitamin C concentration affects urinary excretion of vitamin C in cattle and that plasma vitamin C concentration exceeded the renal threshold for vitamin C in the cows receiving vitamin C at 20 mg/kg of BW per day. Furthermore, increased urinary excretion of vitamin C appears to limit plasma vitamin C concentration in response to vitamin C intake. The daily excretion of vitamin C was estimated by the reported value of daily creatinine excretion, indicating that the daily amount of vitamin C excreted into urine was more than half of supplied vitamin C. Therefore, a large part of supplied vitamin C probably escapes ruminal degradation and is absorbed but excreted into urine.

ABSTRACT. Many animals including cattle can synthesize vitamin C from glucose. The objective of this study was to investigate plasma vitamin C concentration in ketotic cows during the early lactation period because glucose supply for vitamin C synthesis might be limited in these cows. We measured plasma β -hydroxybutyrate (BHBA) concentration in 118 cows within 2 months after parturition. Subclinical/clinical ketosis was quantitatively determined using a plasma BHBA threshold of 1,200 µM. Plasma glucose concentration was lower in the ketotic cows than in the control cows but plasma vitamin C concentration did not differ between the control and the ketotic cows. Then we measured plasma vitamin C, BHBA and glucose levels in 7 cows during the periparturient period. Plasma BHBA increased and plasma glucose decreased after parturition but plasma vitamin C did not change. These results indicate that plasma vitamin C is not related to the incidence of ketosis in the early lactation period. We suggest that ketotic cows have the ability to produce vitamin C to meet its requirement in the early lactation period although glucose supply is not sufficient for milk production. Vitamin C synthesis is possibly given a high metabolic-priority for glucose in lactating cows.KEY WORDS: dairy cow, β -hydroxybutyrate, ketosis, vitamin C.

Plasma vitamin C (ascorbic acid + dehydroascorbic acid) concentration is a good index of the nutritional status of vitamin C. However, the methodologies for storage and analyses have not been investigated in bovine plasma. The validity of an analytical method for bovine plasma using high performance liquid chromatography (HPLC) with a spectrophotometric detector was examined. Exogenous dehydroascorbic acid was almost completely converted to ascorbic acid during the preparation for analysis with a reducing reagent, dithioerythritol. The analytical recoveries of ascorbic acid were high. Ascorbic acid was not detected after treatment with ascorbic acid oxidase. Thus, the specificity of this method is considered to be high. Although vitamin C was stable in plasma treated by dithioerythritol at −20°C for 6 days, vitamin C in untreated plasma significantly decreased during 3‐day storage at −20°C. These results indicate that the HPLC method is suitable for the determination of plasma vitamin C in cattle and that the storage conditions are important for determination of plasma vitamin C. Plasma vitamin C concentration ranged between 1.49 mg/L and 3.33 mg/L in fattening cattle. This result suggests that fattening cattle show large individual variation in plasma vitamin C concentration.

Impaired wound healing is a problem for immobilized patients, diabetics, and the elderly. The 43 amino acid angiogenic peptide thymosin b 4 has previously been found to promote accelerated dermal wound repair in rats, aged mice and db/db diabetic mice, and corneal repair in normal rats. It has been found in great abundance in wound fluid. Here, we hypothesized that thymosin b 4 may regulate matrix metalloproteinase (MMP) expression in cells that are involved in wound repair. Western blot analysis of keratinocytes, endothelial cells, and fibroblasts that were treated with increasing concentrations of thymosin b 4 showed changes in the expression of the MMP-1, À2, and À9. Zymographic analysis of whole excised mouse wounds taken after homogenization also showed changes in MMP-2 and-9 expression over a 3-day period. These results were confirmed in 2-day-old wounds by RT-PCR. We conclude that part of the wound healing activity of thymosin b 4 resides in its ability to increase protease activity. Since thymosin b 4 -induced protease activity can be further controlled by inflammatory cytokines, a regulatory role for thymosin b 4 is proposed in wound healing. These studies suggest that thymosin b 4 may play a pivotal role in extracellular matrix remodeling during wound repair and may be effective in the treatment of chronic wounds in humans.Fluorescence correlation spectroscopy was used to measure the binding and diffusion of growth factors in model extracellular matrices in order to investigate the importance of protein-matrix interactions in regulating signaling molecules within a three-dimensional matrix. Two important growth factors were studied, transforming growth factor b1 and basic fibroblast growth factor, which are known to have specific affinities for fibronectin and the heparansulfate-proteoglycan perlecan, respectively. Collagen-based matrices were prepared by polymerizing type I collagen in the presence of fibronectin or perlecan, and we measured diffusion constants and binding constants of the two growth factors. The binding constant measured for transforming growth factor b1 with fibronectin-containing matrices was in good agreement with that measured using affinity chromatography. However, the interactions measured between fibroblast growth factor and perlecan were significantly weaker than expected. Surprisingly, the strongest interactions by far were with monomeric collagen solutions and fibrillar collagen matrices. Our findings suggest a central role for the three-dimensional fibrillar collagen matrix in growth factor interactions, with modulatory roles for fibronectin or perlecan.