The human umbilical artery presents a capacitative response induced by intracellular Ca2+ stores depletion and expresses transient receptor protein channels type 3 and 6

ENRIQUE N; SALEMME S; SPERONI F; REBOLLEDO A; RIMORINI L; ROLDÁN PALOMO R; PETRUCELLI S; DRUT R; MILESIV

Buenos Aires

Congreso; XXII Congreso Latinoamericano y I Ibero-americano de Ciencias Fisiológicas; 2006

In certain cell types, the depletion of intracellular Ca2+ stores triggers extracellular Ca2+ influx through non-selective cationic channels (NSCC) allowing the refilling of the stores, a phenomenon known as capacitative Ca2+ entry. The aim of this work was to explore the presence of this response in the human umbilical artery (HUA). Intracellular Ca2+ measurement in HUA segments using fura-4AM indicate that treatment with 1 µM thapsigargin, which produces sarcoplasmic reticulum depletion, induced a Ca2+ influx (∆ fluorescence ratio = 0.09 ± 0.01, p<0.05, n=5) which was blunted by 200 µM Gd3+, a NSCC blocker (n=4). Using the single-channel patch-clamp technique in the cell-attached configuration, with a pipette and bath solution containing 140 mM K+, we found that in HUA smooth muscle cells 5 µM thapsigargin increased the open probability of an ionic channel which carried an inward current measuring -0.41 ± 0.16 pA at a membrane potential of -40 mV (n=13). In cells not treated with thapsigargin the activity of this channel did not increase during a 20 min period (n=8). Similar results were obtained with cyclopiazonic acid, which also depletes the sarcoplasmic reticulum (n=9). Transient receptor protein channels (TRPC) are proposed in the literature to be involved in the capacitative response. Hence we studied if they were present in the HUA smooth muscle cells. Using specific antibodies, we demonstrated with immunohistochemical and western blot techniques the presence of TRPC types 3 and 6 and the absence of type 4. We conclude that this artery presents a capacitative response and expresses at least two types of channels which have been implicated in this mechanism