Toffaletti J, Cooper D L, Lobaugh B
Department of Pathology, Duke University Medical Center, Durham, NC 27710.
Metabolism. 1991 Aug;40(8):814-8. doi: 10.1016/0026-0495(91)90008-k.
Because the effects of specific changes in magnesium or protein-bound calcium on biologic processes in humans have not been clearly defined, we developed an experimental system to specifically lower either ionized calcium, protein-bound calcium, or ionized magnesium. As an indicator of the biological effect of these changes, we measured parathyroid hormone (PTH) in blood. To selectively dilute only one constituent, we infused one of four specially prepared solutions into each of six healthy blood donors following ordinary blood donation. Each donor received at random 450 mL of a different solution at four different blood donations. The respective concentrations of ionized calcium (mmol/L), total magnesium (mmol/L), and albumin (g/L) in these fluids were as follows: control fluid, 1.25, 1.20, 40; no calcium fluid, 0, 1.20, 40; no magnesium fluid, 1.25, 0, 40; no albumin fluid, 1.25, 1.00, 0. Using selective in vivo dilution of the volunteers' blood, we specifically lowered either (1) ionized calcium by 0.07 mmol/L (5.5%), (2) protein-bound calcium by 0.09 mmol/L (10%), or (3) ultrafiltrable magnesium by 0.03 mmol/L (4.8%). While measurements of intact PTH showed that concentrations of PTH in blood did not respond to either decreased ultrafiltrable magnesium or decreased protein-bound calcium, these measurements showed that PTH increased by 400% within 10 minutes in response to decreased ionized calcium.
由于镁或蛋白结合钙的特定变化对人体生物过程的影响尚未明确界定，我们开发了一种实验系统来特异性降低游离钙、蛋白结合钙或游离镁。作为这些变化生物效应的指标，我们测量了血液中的甲状旁腺激素（PTH）。为了仅选择性稀释一种成分，我们在六名健康献血者进行常规献血后，向每人输注四种特制溶液中的一种。每位献血者在四次不同的献血中随机接受450 mL不同的溶液。这些溶液中游离钙（mmol/L）、总镁（mmol/L）和白蛋白（g/L）的各自浓度如下：对照液，1.25、1.20、40；无钙液，0、1.20、40；无镁液，1.25、0、40；无白蛋白液，1.25、1.00、0。通过对志愿者血液进行选择性体内稀释，我们特异性降低了：（1）游离钙0.07 mmol/L（5.5%），（2）蛋白结合钙0.09 mmol/L（10%），或（3）可超滤镁0.03 mmol/L（4.8%）。虽然完整PTH的测量结果显示，血液中PTH的浓度对可超滤镁降低或蛋白结合钙降低均无反应，但这些测量结果表明，游离钙降低后，PTH在10分钟内增加了400%。
