CYTOSOLIC CA2+, NA+/H+ ANTIPORT, PROTEIN-KINASE-C TRIO IN ESSENTIAL-HYPERTENSION

The relationships among the cytosolic free Ca2+ (Ca-i), protein kinase C (PKC), and the Na+/H+ antiport may hold the key to unraveling the causes and origin of essential hypertension. Increased cellular Ca2+, accelerated Ca-i turnover rate, or both occur in concert with activation of PKC and the Na+/H+ antiport in a variety of cells. In the vascular smooth muscle cell a rise in Ca-i produces increased tone and in the kidney it enhances sodium retention through stimulation of the Na+/H+ antiport in the renal tubules. In skeletal muscle increased Ca-i and augmented PKC activity produces insulin resistance, which is a major characteristic of essential hypertension. Moreover, elevation of Ca-i in conjunction with increased activities of PKC and the Na+/H+ antiport, may exert trophic effects on the vasculature and the heart, thereby explaining the narrowing of the vascular lumen in peripheral arteries and the cardiac hypertrophy of long-standing hypertension. Because essential hypertension is a common disorder, its evolutionary advantage in primeval times could rest in skeletal muscle, where higher Ca2+ stores and increased Na+/H+ antiport activity enhanced muscular performance and provided a crucial survival element.