SOME EFFECTS OF SULFANILAMIDE ON MAN AT REST AND DURING EXERCISE

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Abstract
At rest and in moderate exercise (5-6 times the resting metabolism) the rate of CO2 elimination is unchanged in human subjects by adm. of sulfanilamide to a blood conc. of 3-4 mg. %. In exhausting exercise there is definitely some handicap in CO2 removal, resulting in the damming back of CO2. This adds to the acidosis of lac-tate formation and results in prolonged dyspnea during recovery. The degree of psychological and general physical handicap observed in subjects taking 2-3 g. of sulfanilamide daily was severe enough to make its prophylactic and therapeutic use unsuitable in patients expected to continue exacting or strenuous work, especially if this requires skill. According to calculations for moderate exercise normal CO2 exchange in the lungs requires sufficient carbonic anhydrase in the red cells to speed the reaction H2CO3 H2O + CO2 75-fold. Independent deductions from previous studies of the inhibitory action of sulfanilamide on dilute enzyme solns. and from present measurements of the enzyme inhibition in the intact red cell suggest that the residual activity in the presence of 3-4 mg. % sulfanilamide is at or near the above threshold. There is some evidence from the measurement of CO2 tensions in the alveoli and in the venous and arterial blood of subjects performing moderate exercise after sufanilamide that the enzyme activity of the carbonic anhydrase is not quite adequate and that the carbamino mechanism may be performing a greater share in the transport of CO2.