SENSITIVITY OF SELECTED IMMUNOLOGICAL, HEMATOLOGICAL, AND REPRODUCTIVE PARAMETERS IN THE COTTON RAT (SIGMODON HISPIDUS) TO SUBCHRONIC LEAD-EXPOSURE

The effect of lead exposure on cellular immunity, hematology, and repr oductive and body condition in mature cotton rats (Sigmodon hispidus) was examined. Two groups of 36 cotton rats each were exposed to 0, 100 , or 1,000 ppm lead in drinking water for either 7 or 13 weeks, betwee n 31 August and 2 December 1990. Specific and non-specific cell-mediat ed immunity was assessed by measuring splenocyte proliferative respons es to polyclonal mitogens (Concanavalin A and Pokeweed mitogen), in vi vo 24-hr delayed-type hypersensitivity, metabolic activity of peritone al macrophages, spleen mass and cellularity, and immune organ developm ent. General physiological condition was assessed from hematological, morphological, and reproductive measures. Immune function was sensitiv e to lead exposure based on depressed proliferative responses of cultu red splenocytes, smaller popliteal lymph nodes, and larger spleens amo ng cotton rats receiving 1,000 ppm lead. Spleen mass was reduced in co tton rats receiving 100 ppm lead. Total leukocytes, lymphocytes, neutr ophils, eosinophils, total splenocyte yield, packed cell volume, hemog lobin, and mean corpuscular hemoglobin were sensitive to lead exposure . Effects of lead exposure on general condition and reproductive param eters included reduced mass of liver, seminal vesicles, and epididymes in males following a 7-week exposure. Histopathologic changes reflect ed lead toxicity and included altered renal proximal tubular epitheliu m, renal intranuclear inclusions, and in some cases, lowered numbers o f sperm and developing follicles. In general, lesions were more pronou nced with increased lead concentration and longer exposure.