AJP - Cell Physiology, Vol 271, Issue 2 C504-C510, Copyright © 1996 by American Physiological Society

ARTICLES

Bovine adrenal endothelial cells express nucleoside transporters nonregulated by protein kinases A and C

R. P. Sen, L. Sobrevia, E. G. Delicado, D. Yudilevich and M. T. Miras-Portugal
Department of Biochemistry, Facultad de Veterinaria, Universidad Complutense, Madrid, Spain.

The present investigation characterizes the nucleoside transporters in bovine adrenomedullary endothelial cells and their possible regulation by the action of protein kinases A and C to establish comparisons with the nucleoside transport system in chromaffin cells. The nucleoside transport proved to be a nitrobenzylthioinosine (NBTI)-sensitive facilitated-diffusion system with high affinity for adenosine. These endothelial cells had a high density of nucleoside transporters (660,000 +/- 130,000 transporters/ cell), measured by NBTI binding, and the efficiency was close to 2 adenosine molecules internalized transporter-1.s-1. The stimulation of the cells with bradykinin and P1,P4-di(adenosine-5')tetraphosphate, which raise the intracellular Ca2+ concentration, did not modulate the adenosine transport. When the cells were stimulated with signals coupled to adenosine 3',5'-cyclic monophosphate intracellular production, such as norepinephrine and isoproterenol, the adenosine transport was not modified. Furthermore, the treatment of the cells with direct activators of both protein kinases A and C had no effect on adenosine transport, in contrast to that reported in chromaffin cells.

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