Publication Date:
2011-08-24
Description:
To determine the influence of dietary calcium on spaceflight-induced alterations in calcium metabolism and blood pressure (BP), 9-wk-old spontaneously hypertensive rats, fed either high- (2%) or low-calcium (0.02%) diets, were flown on an 18-day shuttle flight. On landing, flight animals had increased ionized calcium (P 〈 0.001), elevated parathyroid hormone levels (P 〈 0.001), reduced calcitonin levels (P 〈 0.05), unchanged 1,25(OH)(2)D(3) levels, and elevated skull (P 〈 0.01) and reduced femur bone mineral density. Basal and thrombin-stimulated platelet free calcium (intracellular calcium concentration) were also reduced (P 〈 0.05). There was a tendency for indirect systolic BP to be reduced in conscious flight animals (P = 0.057). However, mean arterial pressure was elevated (P 〈 0.001) after anesthesia. Dietary calcium altered all aspects of calcium metabolism (P 〈 0.001), as well as BP (P 〈 0.001), but the only interaction with flight was a relatively greater increase in ionized calcium in flight animals fed low- compared with high-calcium diets (P 〈 0.05). The results indicate that 1) flight-induced disruptions of calcium metabolism are relatively impervious to dietary calcium in the short term, 2) increased ionized calcium did not normalize low-calcium-induced elevations of BP, and 3) parathyroid hormone was paradoxically increased in the high-calcium-fed flight animals after landing.
Keywords:
Aerospace Medicine
Type:
Journal of applied physiology (Bethesda, Md. : 1985) (ISSN 8750-7587); Volume 92; 1; 3-12
Format:
text
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