The kidney, the repository of waste in the body, is a target organ for mercury. To test the effect of mercury on kidney function, 12 amalgam fillings were placed in the occlusal surfaces of six adult female sheep. In addition, 12 glass ionomer fillings were placed in two other sheep as controls (Am J Physiol, 1990; 258: 939-45).

Kidney function, determined by glomerular filtration rate (insulin clearance), was reduced by 50 per cent within 30 days. Urine potassium levels increased a little while sodium levels showed a greater increase. There was a reduction in albumin a water soluble protein found in blood excreted in the urine. Controls were unaffected.Low sodium levels in the blood stimulate the kidneys to release renin, an enzyme that causes increased blood pressure. When sodium and potassium are not present in their correct ratios, muscle weakness, fatigue and heart irregularities are among the symptoms observed.

Albumin is important for maintaining plasma volume. Changes in albumin ratio adversely affect nutrient distribution to cells. Human studies (Am J Physiol, 1990; 261: 1010-4) have demonstrated

an increase in urinary albumin 12 months after patients with amalgam fillings had them removed suggesting that the kidneys are able to recover from the effects of mercury amalgam.

Data from the UK National Federation of Kidney Patients Association show that kidney disease is on the increase. Some 8000 kidney transplants are made per annum with a waiting list of up to 5000, and 8000 patients are on dialysis. Clearly, mercury poisoning should be suspected as a cause.