Investigations on the effect of different vitamin B-6 supply on vitamin B-6 status (pyridoxine, pyridoxal and pyridoxamine) in liver and body of lactating rats

Eighty female Sprague-Dawley rats were fed a semisynthetic diet during gravidity which was supplemented with 5 mg vitamin B-6 per kg diet. The daily food intake was 14 g. During the following lactation the rats were assigned to one of 10 vitamin B-6 treatment groups (0, 3, 6, 9, 12, 15, 18, 36, 360 and 3 600 mg per kg diet). The feed was given ad libitum. At day 14 of lactation the rats were decapitated. Parameters for determination of the vitamin B-6 status were concentration of pyridoxine, pyridoxal and pyridoxamine in liver and body analyzed by using HPLC. Body was defined without the gastroenteral tract that was divided into carcass (extrahepatical compartments without liver) and total body (extrahepatical compartments plus liver). The mean weight of liver was 13 g with a dry mass of 33 %; there was no difference between the treatment groups. The vitamin B-6 concentration was lowest in rats fed 0 mg vitamin B-6/kg diet (5 mu g/g fresh matter, FM) and highest in the rats fed 3 600 mg vitamin B-6/kg diet (10.9 mu g/g FM). The total vitamin B-6 consisted on the average of 38 % pyridoxal and 62 % pyridoxamine. This was only changed significantly at the highest supplementation level, where 20 % pyridoxine were detected instead of pyridoxamine. The mean weight of carcass averaged 212 g at a dry matter content of 31 %. The vitamin B-6 concentration ranged in the treatment groups from 0 mg to 360 mg vitamin B-6/kg diet between 2.1 mu g/g FM and 2.8 mu g/g FM. It was highest in the 3 600 mg vitamin B-6 treatment group at 7.5 mu g/g FM. The total vitamin B-6 consisted of 63 % pyridoxal and 37 % pyridoxamine. It was only significantly affected in the 3 600 mg vitamin B-6 treatment group, where also pyridoxine could be found in the amount of 56 %. The results indicate that alimentary vitamin B-6 supply had more influence on liver vitamin B-6 concentration than on carcass concentration. Total body concentration is very similar as carcass concentration, as 95 % of vitamin B-6 is located there. The suitability of the parameters for the evaluation of the vitamin B-6 requirement was confirmed by the comparison of two statistical methods. It is concluded that a vitamin B-6 supply of 5 to 6 mg/kg diet is necessary to meet the requirements during lactation.