Vitamin B12 Absorption in Pyridoxine-Deficient Rats

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Abstract
Pyridoxine deficiency in rats results in an impairment of absorption of orally administered vitamin B12. The manner in which the impairment occurs is not fully understood. In this present study, data are presented to determine whether the impairment might be due to the insufficiency of secretion of gastric juice or the atrophy of some endocrine glands. It was found that pyridoxine-deficiency resulted in a lesser secretion of gastric juice and a marked reduction of vitamin B12-binding power. However, the coadministration of vitamin B12 with intrinsic factor, either from stomach homogenate or from rat gastric juice, failed to improve the absorption of orally administered vitamin B12. Studies were conducted to examine the possibility of endocrine dysfunction as a cause of the impairment of vitamin B12 absorption. It was found that in addition to the thyrotrophic hormone the adrenal cortical hormones can affect the absorption of vitamin B12. Thus, hypophysectomy or adrenalectomy impairs the absorption of orally administered vitamin B12. This absorption can be improved by the administration of cortisone to pyridoxine-deficient and stock animals or by injection of ACTH or TSH to hypophysectomized animals. These data taken as a whole indicate that pyridoxine deficiency results in adrenal atrophy, which in turn brings about a decrease in the absorption of vitamin B12.