Document Type

Dissertation

Publication Date

Fall 8-2-1967

Abstract

This study was concerned with the effects of magnesium deficiency produced by dietary means in rabbits. It was designed to make use of recently available tools— atomic absorption spectrophotometry, automated instruments, a radioactive isotope of magnesium, and an apparatus for the in-vitro study of intestinal segments— in order to clarify some of the anomalous observations made in previous studies of magnesium deficiency; to study the effects of such a deficiency on other cations in a variety of tissues and on other constituents of blood; and to study, in the small intestine, in-vitro changes in magnesium, calcium, sodium, and potassium. Rabbits fed a magnesium-deficient diet became moribund within six weeks. The initial acute stage, which lasted up to three weeks and was characterized by neuromuscular signs and a rapid decrease in the concentration of serum magnesium, was followed by a second stage characterized by nutritional failure and a slow rise in the concentration of serum magnesium. Values for ten of twenty-eight constituents measured in the blood of normal rabbits were not previously available. The same constituents measured in the blood of rabbits that had been fed a magnesium-deficient diet for six weeks indicated the presence of electrolyte imbalance and of renal and hepatic damage. The concentrations of magnesium, calcium, sodium, and potassium were determined for 21 tissues in normal and magnesium-deficient rabbits. Information of this scope for such a variety of tissues had not been available previously. In in-vitro studies employing segments of small intestine, radioactive magnesium moved more efficiently across the proximal area than across the distal area and from the mucosal to the serosal surface than in the opposite direction. These results indicate the possibility that the normal rabbit may achieve a net positive balance for magnesium by absorption through the proximal area of the small intestine. The absorption of magnesium was enhanced in both the proximal and the distal areas of the small intestine from magnesium-deficient rabbits. There was no indication in these experiments that absorption of magnesium from the small intestine of rabbits occurs by a process other than passive diffusion.

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