Introduction: Hypertension is a complex disease that affects about 40% of adults worldwide, and is a major risk factor for cardiac hypertrophy and heart failure. Abnormal calcium handling plays a key role in hypertension and cardiovascular disease. In order to function normally cells of the cardiovascular system need to keep intracellular Ca2+ levels under tight control. This is achieved by a number of Ca2+ handling proteins including the plasma membrane Ca2+-ATPase (PMCA). Recent genome wide association studies have shown that single nucleotide polymorphisms in ATP2B1, the gene encoding PMCA1, are strongly linked with hypertension risk. Hypothesis: PMCA1 plays an important role in regulation of blood pressure and protection against hypertension and cardiac hypertrophy. Aims: This thesis aims to examine whether there is a link between PMCA1 and blood pressure regulation, and the development of hypertension. It also aims to determine the impact this link may have on cardiac structure and function. Methods and Results: To study the role of PMCA1, a global PMCA1 heterozygous knockout mouse (PMCA1Ht) was used. Under basal conditions, 3 month old PMCA1Ht mice had about 50% reduction in PMCA1 protein expression compared to the wild type (WT) mice. PMCA1Ht and WT mice had similar blood pressure as measured by tail-cuff method. To study the mice under hypertensive stress conditions, 3 month old PMCA1Ht and WT mice were infused via minipump with angiotensin II. Upon angiotensin II treatment, PMCA1Ht mice showed a significantly greater increase in systolic and diastolic pressure compared to WT mice. Angiotensin II also induced vascular remodelling, with PMCA1Ht mice having greater media thickness and cross sectional area than WT mice. Moreover, PMCA1Ht mice showed a significantly greater cardiac hypertrophic response than WT mice. On the other hand, cardiac function and heart rate were similar in PMCA1Ht and WT mice. While angiotensin II had no effect on PMCA1 expression in the heart, it significantly increased PMCA1 expression in the aortas of both WT and PMCA1Ht mice. More importantly, WT mice had significantly higher PMCA1 expression level than the PMCA1Ht mice treated with the same dose of angiotensin II. This suggests that PMCA1 plays a pivotal role in Ca2+ extrusion in the vasculature and that under stressful conditions PMCA1Ht mice are less able to respond to stress through a compensatory increase in PMCA1 expression, leading to increased intracellular Ca2+ concentration, which in turn leads to increased vascular contractility and increased blood pressure. Conclusion: This work provides evidence that PMCA1 is involved in blood pressure regulation and protects against the development of hypertension and cardiac hypertrophy.