Meeting Abstract
P3.52 Wednesday, Jan. 6 Effects of High Extracellular Zinc on Hemocytes of the Pond Snail, Lymnaea stagnalis RIDGWAY, R.L.*; JAMES III, J.A.; AUDET, E.K.; Seattle Pacific University; Seattle Pacific University; Seattle Pacific University rridgway@spu.edu
Hemocytes plated onto gelatin-coated slides undergo characteristic morphological changes over time that can be divided into stages: I) intitial surface attachment (2-10 min); II) cell flattening/membrane spreading (5-15 min); III) filopodial extension/motility initiation (10-30 min); IV) cell polarization/directional movement (20-60 min). Correlated with these stages are dynamic shifts in cytoskeletal organization, as visualized using fluorescent probes specific for microtubules and microfilaments. Here we examined the effects of extracellular ZnCl2 exposure (range: 10-6 M to 10-3 M) on hemocyte morphology and cytoskeletal organization. In preparations fixed 5 min after plating, 31% of control cells had attained Stage II or greater compared to 12% of 10-4 M and 1% of 10-3 M ZnCl2-exposed cells. At 60 min after plating, 97% of control cells and 90% of 10-4 M ZnCl2-exposed cells had attained Stage II or greater, compared to only 30% of 10-3 M ZnCl2-exposed cells. Differences in the organization of microfilament-based structures were minimal in ZnCl2-exposed cells relative to control cells at the same stage. The distribution and complexity of microtubule networks was impacted in 10-3 M ZnCl2-exposed cells, but this was less evident in 10-4 M ZnCl2-exposed cells. Our results suggest that these immune system cells possess homeostatic mechanisms (e.g., zinc-binding metallothioneins, vesicular sequestration) which maintain cytosolic labile zinc at low levels. The mechanisms appear adequate provided extracellular zinc concentration is less than 10-4 M; higher zinc concentrations can affect cytoskeletal structure and may thus compromise hemocyte function. (Funded in part by a SPU Senior Faculty Research Grant to RLR.)
