RENAL PHOSPHATE EXCRETION IN GOATS

It was the aim of these experiments to characterize further the role o f salivary glands and kidneys in phosphate (P-i) homeostasis of small ruminants. Renal clearance experiments were performed in five female, non-pregnant adult goats during infusions of physiological NaCl or iso tonic phosphate solution. Basal plasma P-i concentrations of 1.6 +/- 0 .3 mM (NaCl infusion) were associated with a renal resorption of the f iltered P-i by 98.5-99.3 % and P-i was excreted in the urine at a rate of 1.2-2.8 mu mol/min. Elevating the plasma P-i levels up to 7.2 +/- 1.7 mM resulted in significant increases of P-i excretion. The mean pl asma threshold for renal P-i excretion of these animals was high (4.3 +/- 1.0 mM) and thus substantially higher than the physiological range of plasma P-i. The maximal tubular resorption rate for P-i in goats w as found to be higher than the respective values in monogastric animal s. In relation to the enhanced P-i concentrations in plasma the saliva ry P-i concentrations increased simultaneously and reached a maximum l evel of about 66.3 mM at plasma levels between 4-6 mM. Indications for hormonal regulation mechanisms via parathyroid hormone (PTH) and calc itriol could not be detected during the infusion periods.