Tissue PH2 measurement for continuous estimation of blood flow changes in rat kidney cortex and medulla

A method is described for estimation of local blood flow changes in the renal cortex and medulla, based on continuous polarographic measurement of tissue pressure of electrochemically generated hydrogen (PH₂). The technique was used in anaesthetized female Wistar rats. The changes in cortical PH₂ were negatively correlated with those in flow velocity in the renal artery (Doppler probe). To evaluate the method, PH₂ responses to a reduction of renal perfusion pressure (RPP) and to angiotensin II were examined. RPP reduction from 130 mmHg to 104 mmHg increased the cortical PH₂ by 3.5% and medullary PH₂ by 6.9% (difference significant at P<0.02). With RPP reduction from 113 mmHg to 76 mmHg the values were 6.9% and 11% respectively (difference significant at P<0.001). Angiotensin II infusion increased cortical PH₂ by 8.7% and medullary PH₂ by 4.1% (difference significant at P<0.005). It is concluded that the method enables continuous estimation of blood flow changes in the renal cortex and medulla.