Vasopressin-induced vasoconstriction: two concentration-dependent signaling pathways

Abstract

Current scientific literature generally attributes the vasoconstrictor effects of [Arg(8)]vasopressin (AVP) to the activation of phospholipase C (PLC) and consequent release of Ca(2+) from the sarcoplasmic reticulum. However, half-maximal activation of PLC requires nanomolar concentrations of AVP, whereas vasoconstriction occurs when circulating concentrations of AVP are orders of magnitude lower. Using cultured vascular smooth muscle cells, we previously identified a novel Ca(2+) signaling pathway activated by 10-100 pM AVP. This pathway is distinguished from the PLC pathway by its dependence on protein kinase C (PKC) and L-type voltage-sensitive Ca(2+) channels (VSCC). In the present study, we used isolated, pressurized rat mesenteric arteries to examine the contributions of these different Ca(2+) signaling mechanisms to AVP-induced vasoconstriction. AVP (10(-14)-10(-6) M) induced a concentration-dependent constriction of arteries that was reversible with a V(1a) vasopressin receptor antagonist. Half-maximal vasoconstriction at 30 pM AVP was prevented by blockade of VSCC with verapamil (10 microM) or by PKC inhibition with calphostin-C (250 nM) or Ro-31-8220 (1 microM). In contrast, acute vasoconstriction induced by 10 nM AVP (maximal) was insensitive to blockade of VSCC or PKC inhibition. However, after 30 min, the remaining vasoconstriction induced by 10 nM AVP was partially dependent on PKC activation and almost fully dependent on VSCC. These results suggest that different Ca(2+) signaling mechanisms contribute to AVP-induced vasoconstriction over different ranges of AVP concentration. Vasoconstrictor actions of AVP, at concentrations of AVP found within the systemic circulation, utilize a Ca(2+) signaling pathway that is dependent on PKC activation and can be inhibited by Ca(2+) channel blockers.

Use of Patch Clamp Electrophysiology to Identify Off-Target Effects of Clinically Used Drugs

“…In support of our hypothesis, celecoxib induced concentration-dependent, endothelium-independent dilation of pre-constricted mesenteric arteries. Similar effects were obtained using known L-type Ca 2+ channel blockers or activators of Kv7 channels (not shown, but see (Henderson & Byron, 2007;Mackie et al, 2008)). The maximum dilatory effect of celecoxib was achieved at a concentration of 20 µM; neither rofecoxib nor diclofenac induced significant artery dilation at the same concentration ( Figure 2B).…”

Differential Protein Kinase C-dependent Modulation of Kv7.4 and Kv7.5 Subunits of Vascular Kv7 Channels

“…Our previous findings, however, strongly support involvement of PKC, a less commonly proposed regulator of M-currents (42,43), in the suppression of endogenous Kv7 currents by physiologically relevant concentrations of AVP. PKC inhibitors calphostin C and Ro-31-8220 prevented AVP-induced constriction of MAs and abolished AVP-induced suppression of Kv7 currents in MASMCs and A7r5 cells, suggesting that AVP acts in a PKC-dependent manner (11,12,27). Furthermore, direct activation of PKC with 1 nM PMA was sufficient to suppress Kv7 currents in both MASMCs and A7r5 cells (11,12).…”

“…Adult male Sprague-Dawley rats were anesthetized with isoflurane and segments of the small intestinal mesentery were surgically removed as described previously (27).…”

Heteromerization of chemokine (C-X-C motif) receptor 4 with α1A/B-adrenergic receptors controls α1-adrenergic receptor function

“…HeLa cells were as described (70). Rat aortic and mesenteric artery VSMC were isolated from male Lewis and Sprague-Dawley rats as described elsewhere (71)(72)(73). All procedures involving rats were in accordance with the Guide for the Care and Use of Laboratory Animals and approved by the Institutional Animal Care and Use Committee of Loyola University Chicago.…”