Endothelin B receptor Ca2+ signaling in shark vascular smooth muscle: participation of inositol trisphosphate and ryanodine receptors

Abstract

[Ca 2+ ]i response to ETBR agonist stimulation by a mean of 39%. These data show for the first time that in VSM of the shark, ETBR activation stimulates both IP3R and RyR, and that cADPR is involved in RyR activation.

Endothelin-1, superoxide and adeninediphosphate ribose cyclase in shark vascular smooth muscle

“…As we reported previously, the response of shark VSM cells to ET-1 at cool temperatures is characterized by a broad peak, which falls back to baseline values in approximately 100·s (Fellner and Parker, 2004). Based on the techniques employed in the present study, we found that the mean baseline [Ca 2+ ] i was 116±6 and the peak response to ET-1 was 220±9·nmol·l -1 (N=53, P<0.01; Fig.·1 2+ are wellstudied inhibitors of the ADPR cyclase in vascular smooth muscle (de Toledo et al, 2000;Sethi et al, 1996).…”

“…Therefore, in the current study we utilized inhibitors of the ADPR cyclase, an inhibitor of NOX and a superoxide dismutase mimetic to investigate how ET-1 might activate the cyclase to generate cADPR. Because our previous investigations of Ca 2+ signaling pathways in shark VSM have demonstrated remarkable concordance with those of mammalian VSM (Fellner and Parker, 2004), we believe that the current study can give insight into the role of superoxide, preserved during evolution, in the responses of VSM to peptide agonists.…”

“…Subsequent experiments were conducted in a temperature-controlled room kept at 18°C. [Ca 2+ ] i was measured as previously described (Fellner and Parker, 2004;Fellner and Parker, 2002). Arterial tissue was placed in an open static chamber and examined in a small window of the optical field of a ×40 oil-immersion fluorescence objective of an inverted microscope (Olympus IX70).…”

“…There are only two reports of cADPR activity in fish, both in oocytes (Polzonetti et al, 2002;Fluck et al, 1999). Recently we demonstrated a role for cADPR in endothelin B receptor (ET B R)-mediated Ca 2+ signaling in the anterior mesenteric artery of Squalus acanthias (Fellner and Parker, 2004). Participation of cADPR in Ca 2+ signaling has been demonstrated from a variety of mammalian vascular smooth muscle (VSM) sources: membrane preparations of rat aorta (Yusufi et al, 2002;de Toledo et al, 2000), renal microvessels , bovine and porcine coronary arteries (Zhang et al, 2004;Yu et al, 2000;Kannan et al, 1996), and pulmonary artery (Wilson et al, 2001).…”

“…Evidence for participation of cADPR in endothelin-1 (ET-1) Ca 2+ signaling has been demonstrated in porcine airway smooth muscle (White et al, 2003), rat seminiferous peritubular smooth muscle (Barone et al, 2002), rat mesenteric artery (Giulumian et al, 2000) and shark mesenteric artery VSM (Fellner and Parker, 2004). None of these studies has explored the mechanism(s) by which ET-1 might activate the ADPR cyclase.…”