Iron absorption and transport mechanisms as related to genetic susceptibility to cotton fur in mink Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/tq57nt417

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  • The "cotton fur" (CF) condition in mink has been shown through investigations at Oregon State University to have three basic causes, viz.: 1) Feeding diets of fish comprising certain species of the cod family, including: Pacific hake, Atlantic whiting and Alaskan pollock; 2) Inclusion of rancid fats in the diet; and 3) Genetic susceptibility of particular strains. This thesis investigates further the cause of CF as it relates to the third factor. Experiments were conducted in two areas and involved, first, a study of iron absorption using ⁵⁹Fe as a tracer in an attempt to determine if genetically susceptible, CF mink are able to absorb adequate dietary iron in a normal manner, and secondly, a study of the iron transport system by electrophoretic separation of the iron carrying proteins (transferring) to determine whether the CF mink differs from normal animals. Iron balance trials conducted at the Oregon State University Radiation Center were designed to investigate possible differences in gastro-intestinal absorption of ferrous iron between mink with an inherent proclivity to CF and normal animals. General methods for these trials followed those used by Bailey (1967). After a single dose of ⁵⁹ferrous sulfate was administered via stomach tube, total urine and fecal samples were collected for a period of seven days. Each sample was weighed, subsampled when necessary and counted to a standard error of one percent with an auto-gamma, deep-well, solid scintillation counter. Three milliliter blood samples were withdrawn from the unanesthetized mink by cardiac puncture periodically after isotope administration and mixed with an anticoagulant. Radioactivity of the whole blood was measured by counting a weighed one milliliter sample. From the remaining whole blood the hematocrit level was determined and the plasma thus separated, was weighed and radioactivity measured. Radioactivity of erythrocytes was calculated from these data. Technical problems encountered in the first two iron absorption trials indicated that presence of food in the gastro-intestinal tract prior to stomach tubing increased absorption possibly by acting to slow passage of the administered isotope. The presence of thiaminase in the fish component of the diet complicated the second trial and injections of thiamine were administered for the final trial. Although absorption was minimal it was concluded that under the conditions of these experiments the anemic CF mink absorbs iron equally as well as its normal counterparts. ⁵⁹Fe absorption followed the pattern expected of normal animals. To establish more definite conclusions about the absorption and metabolism of iron by the CF as compared to the normal mink would require subsequent trials. It was theorized that polymorphism of blood serum transferrins could conceivably account for the iron deficiency anemia observed in CF animals; therefore, the second phase of investigation of this abnormality involved electrophoretic study of these proteins. The disc electrophoresis apparatus and procedures used were patterned from those suggested by Davis (1964) for determining serum types in humans. A polyacrylamide-gel column, formed in a glass tube was composed of three layers: i.e. (1) a large-pore gel containing the serum sample in which electrophoretic concentration of the sample proteins was initiated; (2) a large-pore (spacer) gel in which electrophoretic concentration of the sample proteins was completed; and (3) a small-pore gel in which electrophoretic separation took place. Blood samples were collected by cardiac puncture as before and centrifuged to separate the serum. Three micro-liters of serum were placed in each column of the disc electrophoresis apparatus. A complete serum sample and a sample containing only the transferrin protein fraction prepared by following a precipitation technique described by Sutton and Karp (1965) were analyzed for anemic animals of the CF strain; normal mink of the Cr strain; and normal individuals from an unrelated strain. Proteins of the complete serum were stained with amido schwarz dye and compared visually with the corresponding precipitated serum sample from the same animal. Visual examination of complete, mink serum proteins revealed as many as 10 to 14 dark staining bands of varying thickness and intensities. The transferrins of the precipitated, serum, gel sample appeared as two, closely aligned bands usually corresponding to a single, heavy, dark band in the complete serum sample. Heavy concentration of protein in some cases apparently obscured the two bands. Polymorphism of serum transferrins in mink was not revealed in this study. Visual examination of gel samples indicated that the iron-transport proteins of CF mink were like those of the normal animal under the conditions imposed. Results did not conclusively indicate that such variants of protein do not exist, but it was concluded that any effect would be slight and would probably not be responsible for the CF condition in mink.
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