This project focuses on ionic pathways that lead to increased cytosolic calcium in lymphocytes from a subset of hypertensive patients. Altered cytosolic calcium handling has been demonstrated in blood cells from hypertensive patients. The presence of these abnormalities has supported the hypothesis that ion transport defects may contribute to the pathophysiology of hypertension. Since essential hypertension represents a syndrome sharing a common phenotype, investigations into its pathogenesis must focus on other intermediate phenotypes not shared by all affected individuals. We have found that there is heterogeneity in the levels of lymphocyte cytosolic calcium obtained from hypertensive patients. Steady-state cytosolic calcium levels in hypertensives can be subdivided into at least two distinct modes with about 50 % of hypertensives having levels greater than 120 nM. This elevated basal cytosolic calcium appears to be also associated with hyper-responsiveness to thapsigargin an endosomal Ca2 plus -ATPase inhibitor. These findings have led us to the hypotheses to be tested in this project: abnormal regulation of cytosolic calcium in lymphocytes from some hypertensive patients produces elevated basal and agonist- stimulated levels due to structural or regulatory defects in calcium transport pathways and that these pathways. To address this, we have identified three specific objectives. We will test the hypothesis that, in isolated peripheral lymphocytes from hypertensives, basal cytosolic calcium and its response to agonists is abnormal. We will then immortalize lymphocytes from normal subjects to test the hypothesis that calcium transport pathways which contribute to intracellular calcium homeostasis in immortalized lymphoblasts are similar to those present in isolated lymphocytes. We will use techniques involving spectrofluorimetry and radio labeled calcium to assess calcium influx, efflux and the process which mediate these effects (i.e. Ca 2 plus - ATPase, Na plus -Ca plus exchange and calcium-release activated channels). We will then test the hypothesis that a subgroup of hypertensive patients have abnormalities in these calcium transport pathways present in immortalizedllymphoblasts which contribute to their altered calcium handling. By studying lymphocytes and immortalized lymphoblasts from normal subjects and hypertensive patients with high cytosolic calcium we will produce important information on the presence and site of cytosolic calcium abnormalities in essential hypertension. This information can produce important clues on where potential structural/genetic abnormalities responsible for intracellular calcium homeostasis may be present in patients with essential hypertension.

R03DK053538

1998-05-01

2000-09-29