No abstract

The fact that platelets, PMN leukocytes, and MN leukocytes concentrate ascorbic acid suggests that vitamin C has an important role in their physiological functions. The question still remains as to which one of the cells best reflects vitamin C status. The ascorbic acid content of PMNs and platelets correlates positively with plasma concentration and supplementation with vitamin C, as shown in Evans et al. They also found that MN leukocytes, in contrast, do not show any such relationship; however, MN leukocytes maintain the highest levels of ascorbic acid and play a very important function in immunocompetence. We have found that with a limited number of subjects, ascorbic acid content of MN and PMN leukocytes correlates positively with plasma ascorbic acid, but there was no correlation between platelets and plasma ascorbic acid (unpublished results). Therefore, further work is necessary to evaluate these three blood components for the best cellular marker of vitamin C status. We have developed a reversed-phase HPLC method for ascorbic acid that can be used in conjunction with our cellular differential centrifugation technique for the determination of ascorbic acid in relatively pure blood cell fractions. The chromatographic method is simple, sensitive, and automated. It clearly resolves ascorbic acid, which is the major form of the vitamin found in vivo and is not prone to interference by sugars, carbohydrates, or nucleotides.

Dietary pectin at levels of 0, 3, 6 and 8% was fed ad libitum to rats for 8 wk to evaluate whether the bioavailability of vitamin E fed at 0.001% of the diet was affected by pectin. Rats fed 3% pectin were not different in any vitamin E parameters from those fed 0% pectin. By the end of the study body weights were significantly lower in the 6 and 8% pectin groups after adjusting for their nonsignificant trend of lower food intake. At wk 8, liver vitamin E levels were reduced in the 6 and 8% pectin group compared to values at the start of the study. Both groups had significantly higher red blood cell hemolysis compared to 0% pectin at 8 wk. Fecal fat excretion was not different among the diet groups, but weights of the small and large intestines were significantly increased in rats fed 6 or 8% pectin compared to those fed 0 or 3%. Our results show that 6 and 8 but not 3% dietary pectin decreased vitamin E availability in rats.

SummaryA technique is described for the intermittent collection of blood from the rat tail. By using commonly available equipment, blood samples can easily be obtained from rats without the need for anaesthesia. The development of this technique makes the rat more readily available as an animal model for repeated withdrawals of small blood samples for pharmacokinetic or bioavailability evaluations.