Calcium metabolism and cardiovascular function after spaceflight.
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.
Hatton
Daniel C
DC
Division of Nephrology, Hypertension, and Clinical Pharmacology, Department of Medicine, Oregon Health Sciences University, Portland, Oregon 97201, USA. hattond@ohsu.edu
Yue
Qi
Q
Dierickx
Jacqueline
J
Roullet
Chantal
C
Otsuka
Keiichi
K
Watanabe
Mitsuaki
M
Coste
Sarah
S
Roullet
Jean Baptiste
JB
Phanouvang
Thongchan
T
Orwoll
Eric
E
Orwoll
Shiela
S
McCarron
David A
DA
D000818:Animals; D001792:Blood Platelets / Q000378:metabolism; D001835:Body Weight / Q000502:physiology; D015519:Bone Density / Q000502:physiology; D002118:Calcium / Q000097:blood / Q000378:metabolism*; D002136:Calcium, Dietary / Q000494:pharmacology*; D004032:Diet; D006439:Hemodynamics / Q000502:physiology*; D008297:Male; D051381:Rats; D011918:Rats, Inbred SHR; D013026:Space Flight
D002136:Calcium, Dietary; D002118:Calcium