The purpose of this study is to identify genes that are responsive to paricalcitol (active vitamin D) therapy. Scientists have found that over 30 different types of cells in the body respond to vitamin D therapy, including blood vessels. Low levels of vitamin D may reduce the amount of calcium in the blood, increase the amount of parathyroid hormone (PTH) and cause the parathyroid gland (small gland located in the neck) to get bigger which is called secondary hyperparathyroidism (SHPT). Also, low levels of vitamin D may worsen the heart disease seen in dialysis patients. Paricalcitol, a man-made active vitamin D, is a replacement for vitamin D for preventing and treating SHPT. Studies that followed patients on dialysis have found: (1) differences in death rates between those who received active vitamin D compared with no activated vitamin D, and (2) a survival benefit in chronic kidney disease (CKD) patients receiving paricalcitol, over calcitriol (natural active vitamin D). Researchers have considered that giving paricalcitol to people with (CKD) may also prevent or slow the progression of heart disease.