ZINC EXCHANGE BY ENDOTHELIAL-CELLS IN CULTURE

Endothelial cells form the lining of blood vessels. Therefore, nutrients must cross this barrier each time they enter or leave the blood. While passing through the endothelium, nutrients may interact with intracellular zinc pools. This study was undertaken to characterize the dimensions of the zinc pools that are associated with endothelial cells. Zn-65 was employed as a tracer to follow the pattern of zinc uptake and release by bovine pulmonary aortic endothelial cells that had grown into a confluent monolayer. The total cellular zinc content of the endothelial cells was calculated to be 2.48 nmol zinc/mg protein, based upon specific activity. The t 1/2 cellular zinc turnover was 244 min. Mathematical modeling of both the uptake and the release processes demonstrated that there are two pools of zinc associated with each. A slow exchange pool was estimated to contain approximately 1.4 nmol zinc/mg protein during both influx and efflux experiments. A fast exchange pool contained 1.11 nmol zinc/mg protein during zinc efflux; zinc entering the cell was exchanged rapidly with a pool of 0.65 nmol zinc/mg protein. The efflux measurement may contain labeled ligands resulting from the catabolism of zinc biomolecles that are absent from the influx study; it is more likely to be a true estimate of the fast exchange pool.