A control and data processing instrument for kidney tubule research

A microprocess-based instrument has been designed to facilitate research on the electrical properties of isolated renal tubules. Because of the high correlation between the electrical and ionic properties of tubules, this research helps in understanding the mechanisms of reabsorption and secretion along the many functionally different segments of a renal tubule. By replacing manual methods of control, measurement, and calculation, this instrument expedites the experimental procedure and adds accuracy and flexibility not available in the previous arrangement. Based on operational directives entered by the user, the instrument controls the number, frequency, polarity, intensity, and duration of current pulses through the tubule preparation and records the steady-state voltages induced at either end of the tubule. Then, using a transmission line model, it calculates and displays tubule parameters for each current pulse. The diameter of the tubule, as calculated from the model equations, is of immediate interest to the investigator. How well this figure compares with the physical diameter is an indication of the integrity of the preparation and the validity of the other calculations.