[Laboratory Medicine Learned Through Research on the Pathogenesis of Hypertension]

Laboratory tests used in clinical practice to assess hypertension include a differential diagnosis, the assessment of complications, and detection of adverse events with medication, which cover a variety of fields of laboratory medicine. I learned laboratory medicine through basic and clinical studies on the pathogenesis of hypertension, and summarized those findings and my interpretations. Basic research using animal models points to a causal role of the central nervous system in essential hypertension; however, since clinical research is technically difficult to perform, this connection has not been confirmed in humans. Recently, renal nerve ablation in humans proved to continuously decrease the blood pressure in the presence of resistant hypertension. Furthermore, when electrical stimulation was continuously applied to the carotid baroreceptor nerve of human adults, their blood pressure lowered. These findings promoted the concept that the central nervous system may actually be involved in the pathogenesis of essential hypertension, which is closely associated with excess sodium intake. We demonstrated that endogenous digitalis plays a key role in hypertension associated with excess sodium intake via sympathetic activation in rats. An increased sodium concentration inside the brain activates epithelial sodium channels and the renin-angiotensin-aldosterone system in the brain. Aldosterone releases ouabain from neurons in the paraventricular nucleus in the hypothalamus. Angiotensin II and aldosterone of peripheral origin reach the brain to augment sympathetic outflow. Collectively essential hypertension associated with excess sodium intake and obesity, renovascular hypertension, and primary aldosteronism and pseudoaldosteronism are all suggested to have a common cause originating from the central nervous system.