PT  - JOURNAL ARTICLE
AU  - Ryan M. Fryer
AU  - Jason A. Segreti
AU  - Deborah L. Widomski
AU  - Pamela H. Franklin
AU  - Patricia N. Banfor
AU  - Kristin A. Koch
AU  - Masaki Nakane
AU  - J. Ruth Wu-Wong
AU  - Bryan F. Cox
AU  - Glenn A. Reinhart
TI  - Systemic Activation of the Calcium Sensing Receptor Produces Acute Effects on Vascular Tone and Circulatory Function in Uremic and Normal Rats: Focus on Central versus Peripheral Control of Vascular Tone and Blood Pressure by Cinacalcet
AID  - 10.1124/jpet.107.123901
DP  - 2007 Oct 01
TA  - Journal of Pharmacology and Experimental Therapeutics
PG  - 217--226
VI  - 323
IP  - 1
4099  - http://jpet.aspetjournals.org/content/323/1/217.short
4100  - http://jpet.aspetjournals.org/content/323/1/217.full
SO  - J Pharmacol Exp Ther2007 Oct 01; 323
AB  - Calcium-sensing receptor (CaR) activation decreases serum parathyroid hormone (PTH) and Ca2+ and, despite long-term reductions in mean arterial blood pressure (MAP), may produce acute hypertension in rats, an effect we hypothesized was mediated by constriction of multiple vascular beds. Rats were subjected to 5/6 nephrectomy (NX) or no surgery (Normal); at 7 to 8 weeks, uremia animals were anesthetized and instrumented to record MAP and regional blood flow (carotid, mesenteric, and hindlimb). Cinacalcet [N-(1-naphthalen-1-ylethyl)-3-[3-(trifluoromethyl)phenyl]-propan-1-amine; 1, 3, and 10 mg/kg; 30 min/dose] was infused over 90 min. In NX rats, cinacalcet dose-dependently decreased ionized calcium (iCa2+), elicited a 90% reduction in PTH, and produced dose-dependent self-limiting increases in MAP (from 119 ± 6to129 ± 5, 142 ± 4, and 145 ± 3 mm Hg at the end of each infusion). At 1 mg/kg, carotid vascular resistance (CVR) and mesenteric vascular resistance (MVR) increased to 16 ± 6 and 18 ± 6% above baseline, respectively. Hindlimb vascular resistance (HVR) also trended upward (13 ± 8%). At 3 mg/kg, increases in CVR (38 ± 10%), MVR (40 ± 8%), and HVR (39 ± 14%) were exacerbated; at 10 mg/kg, values remained at or near these levels. The effects of cinacalcet in Normal rats were similar to NX and were attenuated by ganglionic blockade with hexamethonium at low doses but remained significantly elevated at higher doses. Thus, CaR activation acutely increases MAP in uremic and nonuremic rats, responses that occur in parallel to vasoconstriction in multiple vascular beds through both a central and peripheral mechanism of action. Moreover, subsequent mechanistic studies suggest that increases in MAP produced by cinacalcet may be mediated by reduced tonic NO synthase-dependent NO production subsequent to reductions in blood iCa2+. The American Society for Pharmacology and Experimental Therapeutics