A technique has been developed for studying the reactivity of single, isolated resistance vessels, 50 to 250 µ o.d., perfused at constant flow rate. The validity of the method is established because responses to a given stimulating agent are reproducible and stable over a reasonable period of time. The magnitude of the response is dependent on the perfusion pressure, being maximal at a physiological pressure level. Resistance vessels from mesentery and brain of normal rabbits were compared with respect to their threshold for response to several vasoconstrictors. The results reaffirmed the individuality of smooth muscle from different vascular beds. Cerebral and mesenteric vessels are alike in the dose required for threshold constrictor response to KCl, angiotensin and plasma, but differ in that cerebral vessels have a higher threshold for response to epinephrine, norepinephrine and serotonin, and a lower threshold for response to vasopressin, than mesenteric vessels. Since the differences in threshold between vessels from the two sources are not the same for all stimulating agents, it seems probable that smooth muscle of the cerebral vessels is not generally less sensitive to all stimuli than that of mesenteric vessels, but that vessels from the two sources differ in the "number of receptors" for the several vasoactive agents.
Excretion of infused sodium, chloride, and water increased proportionately in patients with progressively more severe grades of hypertension and of increased renal vascular resistance. These relationships held so long as renal plasma flow and glomerular filtration rate were not greatly impaired. The abnormality was characterized by increased renal tubular rejection of sodium, chloride and water.T HAT most hypertensive patients excrete more water, sodium, and chloride than do normotensive patients when given sodium chloride has been well established since the studies of Farnsworth and Barker. Ellis8 also revealed that sodium output correlated with blood pressure. Both basal sodium excretion and excretion under sodium chloride load were higher in hypertensive than in normotensive individuals. Green, Johnson, Bridges, and liehmann9 classified hypertensive patients as " high salt-exeretors " and " normal salt-exeretors. " High salt-exeretors had an elevated output of salt and water, both under basal conditions and under load, an increased salt appetite, nearly normal glomerular filtration rate maintained in the face of reduced renal plasma flow, and a normal cardiac output. Normal salt-excretors had a normal output of salt and water, both under basal conditions and under load, a normal salt appetite, a marked decrease in glomerular filtration rate and renal plasma flow, and a normal cardiac output. It was suggested that sodium output correlated with the filtration fraction. These findings were interpreted as an indication that "high salt-exeretors" represent an earlier stage of hypertensive disease, whereas "normal salt-exeretors" represent a later stage.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.