title: Altered aortic reactivity and lowered blood pressure associated with high calcium intake.
abstract: The hypothesis that dietary calcium (dCa) alters functional properties of aortic smooth muscle in the spontaneously hypertensive rat (SHR) was tested. At 6 wk of age, Wistar Kyoto (WKY) and (SHR) rats were placed on a control diet containing 1% Ca. The experimental SHR group received a 2%-calcium diet. After an average of either 8 or 15 wk on the diets (WOD), aortic rings were prepared for measurement of passive elastic properties and isometric force development. Differences in blood pressure (BP) were not apparent until after 8 WOD when the BP of SHRs on 2% dCa were 10-15 mmHg lower than SHRs on 1% dCa (P less than 0.05). After 8 WOD, when the BP effect first emerged, no significant differences in aortic properties were observed between the SHR groups. However, after 15 WOD, aortas of SHRs on 2% dCa were more compliant than those of SHRs on 1% dCa and between 8 and 15 WOD the sensitivity to KCl decreased in aortas from the WKY group and the SHRs on 2% dCa, but not the SHR-1% dCa group (mean effective dose went from 14.4 +/- 0.4 to 18.5 +/- 0.9 mM for WKY and from 13.6 +/- 0.6 to 17.1 +/- 1.2 mM for SHRs on 2% dCa, P less than 0.05). In addition, between 8 and 15 WOD, a significant decrease in response to a calcium (Ca2+) challenge after removal of K+ and Ca2+ occurred in aortas of the SHRs on 2% dCa, but not in the control diet groups, indicating that a decrease in aortic reactivity was present in the Ca2+-supplemented SHR.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001011:Aorta / Q000187:drug effects*; D001794:Blood Pressure / Q000187:drug effects*; D002136:Calcium, Dietary / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D004548:Elasticity; D006973:Hypertension / Q000178:diet therapy*; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D011918:Rats, Inbred SHR; D011921:Rats, Inbred WKY
chemical_list: D002136:Calcium, Dietary; D011189:Potassium Chloride; D009638:Norepinephrine