DILUTION ACIDOSIS - EVIDENCE FOR A ROLE OF INTRACELLULAR PH IN THE CONTROL OF VENTILATION

Acute hyperosmolality results in an extracellular dilution acidosis an d hypercarbia that does not stimulate ventilatory compensation. The os motic stress is also associated with shifts in water and electrolyte b alance and an increase in intracellular pH. The alkaline intracellular pH was hypothesized to have a role in preventing a normal respiratory response to the extracellular acidosis and hypercarbia. Therefore, th is study examined the effect of ion-exchange blockade on intra- and ex tracellular pH and ventilation during acute hyperosmolality in the Pek in duck (Anas platyrhynchos) by using P-31-nuclear magnetic resonance spectroscopy. Both 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (D IDS) and amiloride inhibited the development of the intracellular alka losis that normally develops in muscle during acute hyperosmolality. I nstead, exposure to hyperosmotic stress during ion-exchange blockade r esulted in a significant acidosis both intracellularly and extracellul arly. Arterial pH decreased 0.10 +/- 0.04 pH unit with a sucrose infus ion after either blocker, and intracellular pH decreased 0.11 +/- 0.06 and 0.16 +/- 0.04 pH units with a sucrose infusion after DIDS and ami loride, respectively. Ventilation increased 79 +/- 28 and 122 +/- 100% , respectively, during acute hyperosmolality after ion-exchange blocka de with either DIDS or amiloride. The results suggest that intracellul ar pH may play a role in the ventilatory response to acid-base perturb ations. The data also indicate that both Cl-/HCO3-, and Na+/H+ exchang es are involved in the development of the intracellular alkalosis duri ng hyperosmotically induced extracellular acidosis.