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Relationship of Selected Cations to Mucosal Amino Acid Absorption and Phosphatase Activity by Isolated Bovine Jejunal Segments^{1, 2,}

University of Arkansas, Fayetteville 72701

Abstract

Two experiments utilizing 24 finished beef animals were conducted to investigate the retionship of calcium, magnesium, potassium and zinc ions at different concentrations to mucosal amino acid absorption and phosphatase activity by isolated jejunal segments of bovine small intestine.

Mucosal amino acid absorption values were significantly lower than those of the controls in the presence of calcium and zinc ions at 50 mM/L concentrations or higher and magnesium at 200 mM/L concentration. The presence of magnesium ions at 100 mM/L or less, and potassium ions at all concentrations studied did not significantly alter mucosal amino acid absorption. The presence of all cations studied at 25 mM/L gave a slight but non-significant increase in mucosal amino acid absorption over that shown by the control. The presence of calcium and zinc ions at 50 mM/L concentrations caused a significant decrease in alkaline phosphatase activity of a mucosal extract, whereas magnesium and potassium ions did not at the same concentration. No effect on enzyme activity was observed in the presence of any of the cations studied at 25 mM/L concentrations. An r value 0.80 between cation inhibition of amino acid absorption and alkaline phosphatase activity suggested that cation inhibition of alkaline phosphatase activity may be a means of inhibiting mucosal amino acid absorption. Acid phosphatase activity was not significantly altered by the cations used at either of the concentrations employed.

¹ Published with the approval of the Director.

² This paper represents part of the Ph.D. dissertation of the senior author, University of Arkansas.

³ Present address: Division of Science, Northeast Missouri State College, Kirksville.