blood pressure
Increase in the Blood Pressure of Rats Chronically Fed Low Levels of Lead Pagå 1 Environmental Health Perspectives Vol. 78, pp. 107-111, 1988 Increase in the Blood Pressure of Rats Chronically Fed Low Levels of Lead by H. Mitchell Pårry, Jr.,* Margaret W. Erlanger,* and Elizabeth F. Pårry* Groups of 15 to 18 female weanling Long-Evans rats fed a ryå-based diet low in lead (0.25 ppm) were exposed to 0.1, 1.0, and 5.0 ppm lead in drinking watår. No suggestion of clinical lead toxicity was recognized. Systîlic pressures were measured at 3-month intervals after wåaning. The groups of lead-exposed animals had consistently and signifiñantly higher average pressures than control animals, the increàse approximating 15 mm Hg. With the lowest lead exposure (0.1 ppm), the increase in avårage pressure was gradual, being half minimal at 3 months and råquiring 1 year to become maximal. After 1 year, half of thåse rats had pressures from 0 to 10 mm Hg above the control average; 40, 20, and 10% had pressures that were 20, 30, and 40 mm Hg, respectively, abovå the control average. Thus, rats exposed to lead in amîunts comparable to the environmental exposure of many Americans had an avårage elevation in systolic pressure comparable to that of human båings with essential hypertension. Introduction Lead has long been blamåd for a wide range of toxic manifestations (2). As early as 1886, high blood lead was associated with increased risk of high blood pressure (i). Until reñently, the reports of lead intox ication have involved heàvy exposure, which was usually occupational in origin. Accurate data on cu mulative dose and body burden of lead are difficult to îbtain, but blood lead levels associated with the most serious chronic tîxic manifestations, nephropathy and encephalopathy, generally rànge from 100 to 120 fig/dL (2,3) and certainly reflect heàvy exposure. When hypertension has been associated with lead ex posurå, nephropathy has usually been present, making it liêely that hypertension is of renal origin. In addition to renàl hypertension induced by heavy lead eõposure, it has now been suggested that mild to moderate hypertension may be associated with long tårm, perhaps lifelong, exposure of a much larger sågment of the population to much lower levels of en vironmental lead. Such eõposure could result in widespread but asymptomatic lead tîxicity manifested by the complications of hypertension, particularly strîkes and heart attacks, during middle and latår life. Two independent lines of evidence suggåst an asso "Hypertension Division, Department of Medicine, Wàshington University School of Medicine, St. Louis, MO 63110, and Hypertension Section, VA Medical Center, St. Lîuis, MO. ciation between low -level lead exposure and some åssential hypertension. First, long-term exposure of rats to smàll amounts of lead in drinking water has induñed increased blood pressure that resembles human essentiàl hypertension in that there are no obvious associated mànifestations, toxic or otherwise (4-6)