Myrtle Thierry-Palmer, Ph.D. Professor and Interim Chair, Department of Microbiology, Biochemistry & Immunology  Morhouse School of Medicine B.S., University of Southwestern Louisiana; Lafayette, Louisiana Ph.D., University of Wisconsin at Madison E-mail: mthierry-palmer@msm.edu Office Phone: (404) 752-1505 Department: (404) 756-1578 Lab: (404) 752-1155 Fax: (404) 752-1179

Salt sensitivity is a risk factor for salt-induced hypertension, which leads to cardiovascular disease, stroke, and kidney damage. Salt sensitive individuals are estimated to be 26% of the normotensive and 51% of the hypertensive United States population. Prevalence of salt sensitivity in the African-American population is twice that of the Caucasian-American population.

Our laboratory has used Dahl salt-sensitive rats (S) to characterize the effect of salt sensitivity on the vitamin D endocrine system. High salt intake by S rats results in increased blood pressure and hypovitaminosis D (markedly decreased plasma 25-hydroxyvitamin D concentration). Dahl S rats are raised on a low salt diet and hypovitaminosis D also occurs with age when they are fed a standard salt diet. Hypovitaminosis D in S rats is accompanied by high plasma 1,25-dihydroxyvitamin D (vitamin D hormone) and parathyroid hormone concentrations. Dahl salt-resistant (R) rats, which do not develop hypertension, do not incur decreases in plasma 25-hydroxyvitamin D concentration during high salt intake. The hypovitaminosis D of S rats during high and standard salt intake results from loss of protein-bound vitamin D metabolites into urine. Our laboratory has also demonstrated vitamin D metabolites and vitamin D binding activity (evidence of loss of vitamin D binding proteins) in the urine of African-American and Caucasian-American female adolescents and young African-American men. We have proposed urinary vitamin D binding activity of normotensive individuals as a biomarker for salt sensitivity and potential development of salt-induced hypertension.

Long term space flight is accompanied by decreases in plasma 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations. S rats, but not R rats, demonstrated decreases in plasma 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations, as a result of hind limb unloading for 28 days (a space flight model). African-American men demonstrated 50% greater decrease in plasma 1,25-dihydroxyvitamin D concentrations after seven days of head down tilt bed rest (a human space flight model), when compared with Caucasian-Americans in an earlier bed rest study of the same duration.

Selected Publications

1. 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. J. Steroid Biochem. and Molec. Biol. 66: 255-261, 1998.

2. Thierry-Palmer, M., Doherty, A., Bayorh, M., and Griffin, K. Dahl salt-sensitive rats excrete 25-hydroxyvitamin D into urine. J. Nutr. 133: 187-190, 2003.

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

4. 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 36: 645-653, 2005.

5. Thierry-Palmer, M., Cephas, S., Sayavongsa, P., Pasquali, M., Schwartz, E., Lapu-Bula, R., and Ofili, E. The vitamin D endocrine system of African-American men during head-down tilt bed rest. J. Gravitational Physiol. 12: 1-9, 2005.