Detection of acetazolamide-induced increase in organ blood flow in rabbits by laser flowmetry.

PURPOSE: We investigated the mechanism by which inhibition of carbonic anhydrase (CA) increases organ blood flow.

METHODS: Regional blood flow (rBF) in white rabbits anesthetized with ketamine/urethane was measured in the kidney, liver, stomach wall, and abdominal muscle by means of laser blood flow probes. Data obtained from rabbits receiving acetazolamide (AZ) to inhibit CA were compared with those obtained from rabbits ventilated with air containing increased concentrations of CO2 .

RESULTS: Systolic blood pressure, body temperature, hemoglobin, and base excess were unaffected by either treatment. Inhalation of CO2 increased blood flow in all organs tested as well as the cardiac output and PCO2 but decreased pH. Inhibition of CA by AZ administration increased the rBF only in the liver and kidney and did not increase cardiac output or decrease pH.

CONCLUSION: Administration of AZ increased rBF in the tissues and organs that contained large amounts of CA without increasing the cardiac output or decreasing the pH, which suggests a direct local effect. A differential sensitivity to the retention of CO2 is suggested as a possible mechanism of the selectivity of the increase in rBF.