Endothelium stimulates the vascular smooth muscle cell Na/K pump of normotensive and hypertensive rats by a protein kinase C pathway.
OBJECTIVE
To investigate the mechanisms involved in the endothelial stimulation of the vascular smooth muscle cell Na/K pump and their possible alteration by hypertension.


METHODS
The Na/K pump activity of vascular smooth muscle cells (VSMC) from normotensive Wistar-Kyoto (WKY) rats and spontaneously hypertensive rats (SHR) was studied using the radioactive analogue of K+ 86Rb+. Conditioned medium of bovine endothelial aortic cells was used to investigate the endothelial modulation of VSMC Na/K pump activity.


RESULTS
Conditioned medium enhanced VSMC Na/K pump activity (ouabain-sensitive 86Rb+ uptake), this effect being higher in SHR cells. This stimulatory effect was neither modified in Na(+)-loaded cells from both rat strains nor inhibited by the Na/H exchange blocker amiloride. Permeable analogues of cyclic adenosine and guanosine monophosphates did not modify the baseline VSMC Na/K pump activity of WKY rats and SHR, and subsequently the guanylate cyclase inhibitor methylene blue did not alter the conditioned medium-induced stimulation of the pump. However, the Ca(2+)-channel inhibitor nifedipine reduced the Na/K pump stimulation by conditioned medium, this decrease being higher in WKY rat than in SHR VSMC. Moreover, treatment with phorbol 12,13-dibutyrate for 24 h or with the protein kinase C inhibitor staurosporine for 15 min reduced the conditioned medium-induced Na/K pump activation in both VSMC cultures.


CONCLUSIONS
Na/K pump stimulation by conditioned medium of endothelial cells is mediated mainly via activation of protein kinase C in VSMC from either WKY or SHR VSMC. However, SHR VSMC show some alterations in their intracellular signalling pathways.
Redondo
J
J
Departamento de Farmacologia y Terapéutica, Facultad de Medicine, Universidad Autónoma, Madrid, Spain.
Rodríguez-Martínez
M A
MA
Alonso
M J
MJ
Salaices
M
M
Balfagón
G
G
Marín
J
J
D000818:Animals; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D004730:Endothelium, Vascular / Q000502:physiology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000201:enzymology / Q000378:metabolism*; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*
D017077:Culture Media, Conditioned; D011493:Protein Kinase C; D000254:Sodium-Potassium-Exchanging ATPase