Diadenosine polyphosphate-induced increase in cytosolic free calcium in vascular smooth muscle cells
Tepel, M.; Bachmann, J.; Schluter, H.; Zidek, W.
Journal of Hypertension 13(12 Pt 2): 1686-1688
1995
ISSN/ISBN: 0263-6352 PMID: 8903633 Document Number: 452196
Objective: To evaluate the effects of two new endogenous vasoconstricting substances, diadenosine pentaphosphate (AP-5A) and diadenosine hexaphosphate (AP-6A) on the cytosolic free calcium concentration in vascular smooth muscle cells. Methods: Spectrofluorophotometric measurements of cytosolic Ca-2+ were conducted in monolayers of cultured rat vascular smooth muscle cells using the calcium-sensitive fluorescent dye fura-2. Results: The resting Ca-2+ concentration in vascular smooth muscle cells was 80 +- 5 nmol/l (mean +- SEM; n = 39). The addition of 10 mu-mol/l AP-5A or AP-6A significantly increased Ca-2+ in vascular smooth muscle cells to 248 +- 55 and 358 +- 124 nmol/l, respectively. The sustained increase in Ca-2+ after administration of AP-5A or AP-6A was 143 +- 40 and 148 +- 57 nmol/l, respectively. Diadenosine polyphosphates induce a transplasmamembrane calcium influx as detected by experiments in the absence of external calcium or by using the manganese quenching technique to report unidirectional calcium fluxes. The effects of diadenosine polyphosphates were compared to those of the well known vasoconstrictor angiotensin II, which increased Ca-2+ in vascular smooth muscle cells by 1053 +- 174 nmol/l. Conclusions: Diadenosine polyphosphates increase Ca-2+ in vascular smooth muscle cells, thereby regulating the contractility of vascular smooth muscle and subsequently blood pressure.