Use of ultrafiltration probes in sheep to collect interstitial fluid for measurement of calcium and magnesium.

Studies of calcium and magnesium changes in living animals usually involve blood, urine, and fecal samples. These samples provide only information on whole-body averages and give no indication of differences between tissues. Ultrafiltration probes were developed to sample interstitial fluid from muscle, bone, and subcutaneous tissue of sheep to provide a tool for investigating tissue differences in calcium and magnesium concentrations. The potential of the probes for mineral distribution studies was demonstrated in sheep by using infusion of a calcium gluconate solution.