McCoy M A
Department of Agriculture and Rural Development for Northern Ireland, Stormont Belfast BT 4 3SD, Northern Ireland.
Magnes Res. 2004 Jun;17(2):137-45.
Magnesium deficit has been associated with many sub-clinical and clinical conditions in humans and animals. The incidence of hypomagnesaemia is high in lactating cows grazing spring pastures, occasionally resulting in the often fatal condition known as grass tetany. While plasma magnesium concentrations can be used to assess magnesium status in the live animal, post-mortem diagnosis of clinical grass tetany is difficult. Recent studies have investigated the potential of eye fluid magnesium concentration as a post-mortem marker of hypomagnesaemic tetany. In tetany induction studies carried out in adult ewes and lactating cows significant relationships were found to exist between the concentrations of magnesium in either cerebrospinal fluid or plasma and either aqueous or vitreous humour. In freshly dead animals aqueous humour magnesium concentrations of < 0.33 mmol/L in adult sheep and < 0.25 mmol/L in adult cattle were associated with severe hypomagnesaemia and tetany. However, aqueous humour was found to be unstable post-mortem. Vitreous humour was considerably more stable and a vitreous humour magnesium concentration in adult sheep of < 0.65 mmol/L for up to 24 hours post-mortem or < 0.55 mmol/L in adult cows for up to 48 hours was associated with severe hypomagnesaemia and tetany. Provided clear-fluid samples are taken from appropriate animals and processed correctly in the laboratory, the concentration of magnesium in vitreous humour is a useful and practical marker in the post-mortem diagnosis of hypomagnesaemic tetany in ruminants.
镁缺乏与人类和动物的许多亚临床和临床病症有关。在放牧春季牧场的泌乳奶牛中，低镁血症的发生率很高，偶尔会导致一种通常致命的病症，即青草搐搦。虽然血浆镁浓度可用于评估活体动物的镁状态，但临床青草搐搦的死后诊断很困难。最近的研究调查了眼液镁浓度作为低镁血症搐搦死后标志物的潜力。在对成年母羊和泌乳奶牛进行的搐搦诱导研究中，发现脑脊液或血浆中的镁浓度与房水或玻璃体液中的镁浓度之间存在显著关系。在刚死亡的动物中，成年绵羊房水镁浓度<0.33 mmol/L，成年牛<0.25 mmol/L与严重低镁血症和搐搦有关。然而，发现死后房水不稳定。玻璃体液则稳定得多，成年绵羊死后24小时内玻璃体液镁浓度<0.65 mmol/L或成年奶牛死后48小时内<0.55 mmol/L与严重低镁血症和搐搦有关。只要从合适的动物身上采集清亮液体样本并在实验室中正确处理，玻璃体液中的镁浓度就是反刍动物低镁血症搐搦死后诊断中一种有用且实用的标志物。
