Plasma Parathyroid Hormone and Insulin Concentrations in Cows Administered Potassium Chloride and Sodium Citrate

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Abstract
Two age groups of nonpregnant cows were used to study plasma changes in parathyroid hormone, insulin, and glucose, and renal clearance rates of magnesium, calcium, and inorganic phosphorus after intraruminal administration of 1.5 g potassium chloride (KCl)/kg body weight (BW) or 1.5 g sodium citrate/kg BW. Magnesium (2.4 mg/kg BW) was simultaneously infused intravenously for 120 minutes to facilitate the measurement of changes in magnesium clearance rate and kidney tubular resorption due to the treatments. Elevated plasma concentrations of potassium from intraruminal infusion of KCl increased plasma parathyroid hormone, insulin, glucose, and magnesium levels. Net tubular resorption of magnesium (TMg) was also increased after potassium dosing, and the old cows had lower TMg values compared with the young cows. Plasma magnesium and calcium clearance rates were increased only by citrate, while phosphorus was not influenced by either treatment. These results provide evidence for a relationship between potassium and the endocrine factors, parathyroid hormone, and insulin; citrate appears to antagonize tubular resorption of magnesium and calcium.