Experimental Designs for the Distribution-Free Analysis of Enzyme Kinetic Data

EFFECT OF SERUM ON SODIUM PUMP ACTIVITY AT VARIOUS CONCENTRATIONS OF INTERNAL AND EXTERNAL SODIUM IN MOUSE (3T3) AND HUMAN (HeLa) CELLS

“…The normal and high [Na]i values were around 18 and 120 mmol/l cell water respectively. The Km and Vmax parameters were estimated by the two-point method of Duggleby, 1981 conditions. We can conclude then that the serum effects described earlier are due to changes in Vmax.…”

“…The extracellular space was washed six times in around 15 s with Krebs solution at 2°C , so reducing the Na concentration to a negligible level with minimal changes in the concentration of intracellular ions (Lamb & McCall, 1972), and then the influx measured over1 min at 37 'C. The temperature rise from 2 to 37 'C was achieved by rapid rinsing with Krebs solution at 37 'C, and occurred with a T1 of around 5 ms and reached completion in 20 ms ( (Duggleby, 1981). As the variance is roughly proportional to the absolute value in this system, the higher value used was 5 mm and the lower value 0 5 mm in normal Na mediumn and 005 mm in low Na medium.…”

“…4). In these circumstances the best estimate of Km and Vmax is obtained b-y doing multiple estimates of K influx at two values of extracellular K concentration ([K]O) (Duggleby, 1981). As the variance is roughly proportional to the absolute value in this system, the higher value used was 5 mm and the lower value 0 5 mm in normal Na mediumn and 005 mm in low Na medium.…”