Figure 3. Effect of decreases in extracellular sodium concentration on arteriolar myogenic constriction and active force development.

A, impact of lowering extracellular sodium concentration on afferent arteriolar myogenic constriction. ○, •, ▿ and ▾ represent 140, 100, 70 and 50 mm sodium in the media, respectively. * Significant difference from respective basal value at 80 mmHg. B, effects of varing extracellular sodium concentrations on afferent arteriolar active force development at a renal arterial pressure of 160 mmHg. Active arteriolar force was calculated from changes in diameters, and is expressed as percentage changes from passive tension of each arteriole at 160 mmHg. Data from single afferent arterioles are connected with dotted lines. Continuous line indicates the best-fitting curve for a total of 28 data points obtained using regression analysis:

(tolerance < 0.0001), where [Na⁺] indicates extracellular sodium concentration.