Intracellular Ca2+ and force generation determined in resistance arteries of normotensive and hypertensive rats.
OBJECTIVE
Dysfunctional cellular Ca2+ handling has been proposed to underlie the heightened vascular reactivity observed in the spontaneously hypertensive rat (SHR) model of genetic hypertension. We tested the hypothesis that basal or agonist-induced mobilization of intracellular Ca2+ is elevated in mesenteric resistance arteries of SHR compared with the normotensive Wistar-Kyoto (WKY) rat.


METHODS
A method using fura-2 for the simultaneous measurement of intracellular Ca2+ and isometric force generation in isolated mesenteric resistance arteries was employed to measure agonist-induced changes in Ca2+ and force during activation with 100 mmol/l K+ or 10 mumol/l norepinephrine. Arteries with normalized diameter 220-240 microns from male rats aged 14-15 weeks were examined.


RESULTS
No differences were detected between the rat strains in basal Ca2+ concentration or the steady-state concentration of Ca2+ achieved in response to either 100 mmol/l K+ or 10 mumol/l norepinephrine. The relationship between Ca2+ and force during the contractile responses to K+ and norepinephrine was analyzed. No differences between the strains in the level of active stress, normalized to unit intracellular Ca2+, were detected in the steady-state responses to K+ or norepinephrine.


CONCLUSIONS
The present results do not support the hypothesis that alterations in either the basal concentration of intracellular Ca2+ or the amount of intracellular Ca2+ mobilized in response to high levels of norepinephrine or K+ are present in resistance arteries of SHR compared with those of WKY rats. Moreover, these findings suggest that elevations in Ca2+ do not contribute to heightened peripheral resistance in SHR.
Bukoski
R D
RD
Department of Internal Medicine, University of Texas Medical Branch, Galveston 77550.
Lastelic
B A
BA
Xue
H
H
Li
J
J
Bian
K
K
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D007425:Intracellular Membranes / Q000378:metabolism*; D008297:Male; D008638:Mesenteric Arteries / Q000187:drug effects / Q000378:metabolism / Q000503:physiopathology*; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY; D012016:Reference Values; D014655:Vascular Resistance; D014661:Vasoconstriction / Q000502:physiology*
D011188:Potassium; D002118:Calcium; D009638:Norepinephrine