36Cl- and 86Rb+ uptake in rat parotid acinar cells

36Cl- uptake was markedly (85 per cent) inhibited by the loop diuretics, furosemide and bumetanide. Partial replacement of Na+ in the incubation medium (from 137 to 5 mM) reduced 36Cl- uptake 30 per cent; total replacement reduced uptake to 40-45 per cent of control values. Partial replacement of K+ (from 5.8 to 1 mM) decreased 36Cl- uptake approx. 45 per cent; complete replacement resulted in minimal levels of 36Cl- uptake (less than 10 per cent of controls). Ouabain reduced 36Cl- uptake approx. 55 per cent in the absence of bumetanide, but was without effect in its presence. 86Rb+ uptake was reduced approx. 85 per cent with bumetanide; complete replacement of Cl- with I- or gluconate-, decreased 86Rb+ uptake by 55 or 40 per cent respectively. The results support the notion that the bulk of Cl- influx in rat parotid acinar cells is via a loop diuretic-sensitive Na+/K+/Cl- co-transport mechanism as may occur in other secretory epithelia.