FLOW CYTOMETRIC MEASUREMENTS OF NEURONAL DEATH TRIGGERED BY PCBS

We have examined the effects of several individual polychlorinated bip henyl (PCB) congeners and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) o n viability and intracellular calcium concentration in acutely dissoci ated cerebellar granule cell neurons obtained from 7-14 day old rat pu ps, using a flow cytometer. Cell death was determined using the fluore scent dye, 7-aminoactinomycin-D (7-AAD), while intracellular calcium c oncentration was determined using Fluo-3-AM. When acutely isolated neu rons were exposed to 2,4,4' trichlorobiphenyl (2,4,4'), there was a do se- and time-dependent loss of viability beginning within 5 min. At a concentration of 100 mu M, 80% of neurons were dead within 45 min. Los s of viability was preceded by an apparent increase in cell granularit y. No significant cell death was observed upon exposure to the highly dioxin-like coplanar PCB, 3,4,5,3:4: at a concentration of 100 mu M or by TCDD at a concentration of 0.1 mu M. A slight loss of viability wa s seen with the ortho 2,6,2',6' and the coplanar 3,4,3:4: but for both it was small. All of the PCB congeners caused an early, transient inc rease in intracellular free calcium concentration, although TCDD did n ot. A small, late increase in intracellular free calcium was seen with 2,4,4: probably reflecting events leading to loss of viability. We co nclude that at least one PCB congener, 2,4,4: is very neurotoxic and c an cause rapid death of cerebellar granule cells. (C) 1997 Inter Press , Inc.