title: Renal tissue impedance: responses of the real and imaginary component to experimental variations in medullary electrolytes.
abstract: In order to assess the renal corticomedullary electrolyte gradient, electrical impedance (zeta) and phase angle (phi) were measured in the in-situ kidney of anaesthetized rats. A set of platinum/iridium needle electrodes was used, and the frequency (f) of the measuring current was varied between 0.5 and 50 kHz. zeta and its imaginary component (chi c) fell sharply as f increased from 0.5 to 3.5 kHz, and then decreased slowly or stabilized, whereas the real component (R) decreased progressively over the entire f range. Ion concentration in the renal medulla was experimentally lowered by administration of furosemide or hypertonic mannitol or by inducing a haemorrhage, and raised by infusing hypertonic NaCl solution. Both R and chi c varied inversely with tissue electrolyte concentration. Raising f from 3.5 to 10 and further to 20 kHz did not significantly amplify the changes in zeta. Within this frequency range R was not a more sensitive index of tissue electrolyte changes compared with overall zeta-value. The results verify previous empirical data indicating that changes in medullary tissue electrolytes can be dynamically estimated by monitoring tissue impedance.
authors.affiliation: Department of Applied Physiology, Medical Research Centre of the Polish Academy of Sciences, Warsaw.
authors.forename: J
authors.initials: J
authors.lastname: Sadowski
authors.forename: W
authors.initials: W
authors.lastname: Niewiadomski
authors.forename: S N
authors.initials: SN
authors.lastname: Rasmussen
mesh_terms: D000818:Animals; D004594:Electrophysiology; D005665:Furosemide / Q000494:pharmacology; D006982:Hypertonic Solutions; D007679:Kidney Medulla / Q000502:physiology*; D008297:Male; D008353:Mannitol / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012965:Sodium Chloride / Q000494:pharmacology; D014882:Water-Electrolyte Balance / Q000187:drug effects
chemical_list: D006982:Hypertonic Solutions; D008353:Mannitol; D012965:Sodium Chloride; D005665:Furosemide