Numerous hypotheses have been suggested to account for the development of primary hypertension in man (1), including salt (NaCl) intake, overall nutrition, and genetic make-up (1, 2). It has also been proposed that increased blood pressure is due to a supersensitivity of blood vessels to the constrictor actions of endogenous neurohumoral substances (for example, adrenergic amines, angiotensin, or vasopressin) or to a decreased sensitivity of blood vessels to endogenous vasodilator substances (for example, prostaglandins) (1). All of these hypotheses have generated some controversy, and exactly how a sustained increase in arteriolar and venular vascular tone is brought about in a variety of clinical and experimental forms of hypertensive disease remains a mystery (1).
Several recent studies point to a causal relation between decreased concentrations of magnesium ion (Mg.sup.2+.) in blood or tissues and hypertension; the incidence of hypertension is high in geographic areas with soft drinking water or magnesium-poor soil (3-6). Since 1925, it has been known that pharmacologic does of magnesium salts can somehow produce hypotension and attenuate high blood pressure in hypertensive patients; more recently, long-term administration of lower doses of magnsium salts has decreased requirements for antihypertensive drugs (7). Hypomagnesemia has been r eported in a number of hypertensive ve patients in different geographic areas (8).
Artificial lowering of the Mg.sup.2+ content of isolated coronary, cerebral, and peripheral blood vessels from rats, rabbits, piglets, and dogs, as well as man, induces rapid, contractile responses and potentiates the actions of a variety of neurohumoral constrictors agents, including adrenergic amines and angiotensin (9). Acute hypermagnesemia inhibits the spontaneous tone of arteries and veins both in vitro and in intact animals, and decreases arterial resistance to blood flow (9, 10). Thus, evidence is accumulating to suggest that extracellular Mg.sup.2+ plays a critical role in the regulation of vasomotor tone.
It has been suggested that...