Human G protein beta 3 subunit variant does not alter hypercarbic or hypoxic ventilatory response

Hypercarbic respiratory drive is mainly determined by P-CO2 and pH with act ivity of the intracellular Na+/H+ exchanger (NHE) playing an important role in maintaining intracellular pH and respiratory drive. Because NHE activit y varies with genetically different G-protein beta3 subunits (GNB3) (C/T po lymorphism at nucleotide position 825) different genotypes might alter resp iratory regulation. To test the hypothesis that short-term ventilatory resp onses vary with different GNB3 healthy volunteers with different genotypes (CC, TC, TT) were exposed to either hyperoxic hypercarbia (n=33) or to isoc apnic hypoxia (n=31), respectively. There was no difference between CC, TC, and TT genotypes in hypercarbic and hypoxic respiratory drive when assesse d as the ratio of minute ventilation over endexpiratory P-CO2 changes (Delt a (V) over dot .E/Delta PETCO2), maximal tolerable PETCO2, and ratio of cha nges in ventilation over arterial haemoglobin desaturation (Delta (V) over dot . (E)/DeltaS(O2)), respectively. Thus, short-term hypercarbic and hypox ic ventilatory drive do not differ between individuals with genotypes encod ing different GNB3. Whilst respiratory control may still be influenced by G -protein aberration, other mechanisms seem to have a more important role in controlling ventilation.