Doctoral Dissertations

Date of Award

8-1967

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Animal Science

Major Professor

R.G. Cragle

Committee Members

R.H. Feinberg, J.T. Miles, R.L. Murphree, E.W. Swanson

Abstract

The translocation of substances from the lumen of the intestine into the blood or into extracellular space (absorption) is a complex phenomenon. Any process such as active transport, carrier-facilitated diffusion, diffusion across lipid layers or through pores, vesiculation or pinocytosis can be assumed to be involved in this translocation. The involvement of one or more processes in the absorption of a particular constituent often produces experimental results that are difficult to interpret. All of the factors involved in absorption will not be resolved until the structure of biological membranes is better understood. Knowledge of membrane structure is essential before the biologist can relate, with validity and reliability, structure to function, that is, intestinal epithelial cells to their function of absorption. Structural-functional relationships of membranes precedes an understanding of the organism's ability to exert physiologic control over a particular function. Obviously, the main function of the cell membrane is to maintain an organized intracellular environment consistent with its genetic direction. Studies concerned with the transfer of metabolites across cell membranes are of secondary importance only to the biosynthesis of the membranes themselves.

One of the most prominent environmental situations presented to the intestinal epithelial cell is the ionic composition in the ingesta. Since the ingesta does not possess the ionic constancy of body fluids, variability in absorption of a particular metabolite is not only often encountered but probably should be expected. The effects of ionic environment have been investigated particularly in connection with the absorption of sugars.

Basically, this study represents a modest attempt to define the effects of some physical conditions in the intestinal lumen and their effects on the passage of certain cations in vivo. The objectives of this study were: (1) to determine the concentration of some inorganic constituents in the gastrointestinal tract of calves, (2) to compare the insorption of calcium, strontium, sodium, and potassium from jejunal and ileal segments of calves, (3) to determine the effects of ionic calcium and strontium alternation on subsequent insorption of these cations to the blood, (4) to determine the effects of hypertonic conditions in the lumen on the insorption of some major cations, and (5) to determine the effects of iodoacetate on the relative passage of calcium and strontium.

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