Research Interests

The investigator is conducting studies to characterize salt sensitivity and to determine the underlying mechanisms involved in the alterations in the calcium endocrine system of Dahl salt-sensitive (S) rats. High salt intake results in increased blood pressure and plasma parathyroid hormone (PTH) concentration and markedly decreased plasma 25-hydroxyvitamin D and 24,25-dihydroxyvitamin D concentrations in S rats, but not in salt-resistant (R) rats. Our recent study indicates that S rats, but not R rats, excrete 25-hydroxyvitamin D and 25-hydroxyvitamin D binding protein(s) into urine during low salt intake. This excretion increases during high salt intake. S rats also excrete more calcium into urine than R rats when fed a standard diet. Long term high salt intake will likely have a greater effect on the skeletal system of S compared with R rats, because of the effects of salt sensitivity on calcium and vitamin D metabolism.

Long term space flight is accompanied by loss of bone mass. This loss has been ascribed to a mechanical bone adaptation to weightlessness. There is no evidence that the loss of bone is completely reversed on return to Earth. It is necessary thus to devise countermeasures to bone loss in long term space travel. The investigator is currently engaged in studies to determine the effects of salt sensitivity on bone loss when rats are hind limb unloaded (space flight model).
The investigator is also examining the effect of head down-tilt bed rest (a human space flight model) on the calcium endocrine system of African-American males. These projects have relevance to salt-sensitive individuals, estimated to be twenty-five percent of the United States population, and particular relevance to the black American population, because of its higher rate of salt sensitivity.

Relevant Publications

Thierry-Palmer, M., Cephas, S., Sayavongsa, P., Doherty, A., and Arnaud, S.B. Dahl salt-sensitive rats develop hypovitaminosis D and hyperparathyroidism when fed a standard diet. Bone 2005; 36:645-653.

Thierry-Palmer, M., Cephas, S., Cleek, T., Sayavongsa, P., and Arnaud, S.  The response of Dahl salt-sensitive and salt-resistant female rats to a space flight model. Journal of Gravitational Physiology 2003; 10:39-46.

Thierry-Palmer, M., Doherty, A., Bayorh, M.A., and Griffin, K.  Dahl salt-sensitive rats excrete 25-hydroxyvitamin D into urine.  Journal of Nutrition 2003; 133:187-190.

Faqi, A.S., Sherman, D.D., Wang, M., Pasquali, M., Bayorh, M.A., Thierry-Palmer, M.  The calciuric response to dietary salt of Dahl salt-sensitive and salt-resistant female rats.  American Journal of the Medical Sciences  2001; 322:333-338.

Thierry-Palmer, M., Carlyle, K., Williams, M., Caines-McKenzie, S., Bayorh, M., Tewolde, T., Emmett, N., Harris-Hooker, S., Sanford, G., and Williams, E.   Plasma 25-hydroxyvitamin D concentrations are inversely associated with blood pressure of Dahl salt-sensitive rats.  Journal of Steroid Biochemistry and Molecular Biology 1998; 66:255-261.

Keywords
Vitamin D, Calcium, Hypertension, Bone, Salt-Sensitivity