Long-Term Blood-Pressure Monitoring in Unrestrained Animals

The kidneys are not only intimately involved in the long-term regulation of blood pressure (BP), but hypertension per se leads to secondary alterations in renal function (1 –4 ). Moreover, the kidneys are a major target site for end-organ hypertensive damage. Indeed, hypertension plays a dominant role in the progression of all forms of chronic renal diseases, including diabetic nephropathy (5 –9 ). An accurate estimate of the ambient BP load is critical in defining the relationships between BP and renal damage in and between experimental models or to evaluate the impact of any therapeutic intervention on such relationships (9 ). Additionally, the interrelationships between renal function, BP regulation, and hypertensive renal damage involve complex interactions between genetic and environmental factors that are the subject of ongoing investigations and which require rather precise and accurate characterization of the BP phenotype for valid conclusions (10 –16 ). However, BP exhibits moment-to-moment fluctuations as a result of the activity and interactions of neural, hormonal, and other components of the cardiovascular system in addition to the circadian rhythms (17 ,18 ). Such BP lability is further exaggerated in hypertensive states (17 –19 ). Therefore, conventional periodic tail-cuff BP measurements, although adequate for separating relatively large differences in average BP between experimental groups, are inherently inadequate in providing an accurate assessment of the ambient BP profiles that are usually necessary to define the relationship of BP to the parameters of investigative interest (19 –22 ).