Ectoadenylate kinase and plasma membrane ATP synthase activities of human vascular endothelial cells.

Formation of ATP from ADP on the external surface of vascular endothelial cells has been attributed to plasma membrane ATP synthase, ectoadenylate kinase (ecto-AK), and/or ectonucleoside diphosphokinase. These enzymes or their catalytic products have been causatively linked to the elaboration of vascular networks and the regulation of capillary function. The amount of ATP generated extracellularly is small, requiring sensitive analytical methods for quantification.

Estimating the number of viable animal cells in multiwell culture--a tetrazolium-based assay.

A reliable, indirect method (GPD/INT assay) for estimating the number of live animal cells in multiwell culture has been devised. It is based on the glucose-6-phosphate dehydrogenase (Gpdh) and 6-phosphogluconate dehydrogenase activities present in the cytoplasm of viable eukaryotic cells but not in their bathing medium nor in nonviable cells. A single reagent mixture, buffered at pH 7.