Brief Review Flow Regulation of Vascular Tone Its Sensitivity to Changes in Sodium and Calcium

Ahypotheses concerned with the basis of human or animal models of hypertension must provide an explanation of the increase in peripheral vascular resistance — the common attribute of the hypertensive state. They must also provide experimental evidence for, or at least contain a reasonable suggestion regarding the basis of, the decreased diameter of the small arteries and possibly small veins seen in this condition. Furthermore, these causative processes should be of sufficient magnitude to account for the decreased diameter. Possible causative mechanisms have frequently been investigated in isolated blood vessels. Usually, the vascular tissues studied —in vitro preparations, cultured vascular smooth muscle cells, or subcellular biochemical fragments — have originated from the larger, usually elastic arteries (see below). Research has emphasized the effects of contractile agonists of various types, cellular depolarization, perivascular nerve activation, and various experimental manipulations of the ionic environment.