Surrogate data analysis of renal tubular pressure fluctuations in hypertensive rats

摘要

Abstract: We observed previously that hydraulic pressure in rat renal proximal tubules changes from the periodic oscillations found in normal animals to random-appearing fluctuations during the development of hypertension. It was suggested that the random- appearing fluctuations seen in the hypertensive rats were due to chaotic dynamics in the systems regulating tubular pressure and flow. To test this hypothesis we have now produced surrogate data sets from the originals by randomizing the phase of the power spectra. We have applied both correlation dimension estimation and forecasting error as discriminating statistics. The results show that the original experimental time series can be distinguished from linear and static nonlinear correlated noise, which confirms that the nonlinear behavior is due to the intrinsic dynamics of the system. This finding suggests that there is a low dimensional chaotic attractor that governs renal hemodynamics in the hypertensive stage. To our knowledge this represents the first rigorous demonstration of a transition to chaotic dynamics in an integrated physiological control system occurring in association with a pathological condition.!18