Inhibition of 36Cl uptake by stilbene sulphonic acid derivatives and loop diuretics in rat submandibular salivary acini.

Acini were isolated from submandibular glands by enzymatic digestion and incubated in HCO3-containing and HCO3-free [hydroxyethyl-1-piperazine-ethane sulphonic acid (HEPES) buffered] solutions to compare the accumulation of the isotopic tracer 36Cl in the absence and presence of stilbene sulphonic acid derivatives and of loop diuretics. Tracer accumulation was similar in both solutions in the absence of inhibitors and reached 17-19 nmol/mg protein after 5 min of incubation. Exposure to 10(-3) M 4,4'-diisothiocyano-2,2'-stilbene disulphonic acid (DIDS) or to 10(-4) M bumetanide in HCO3-buffered medium resulted in significant reductions in both the initial phase (from 0 to 5 min) and the steady-state phase (5-30 min) of 36Cl accumulation. By contrast, in HCO3-free, HEPES-buffered incubation solution, DIDS was significantly less effective in reducing 36Cl accumulation, while bumetanide was somewhat more effective than in HCO3-buffered medium. At a higher dose (10(-3) M), furosemide was less effective than bumetanide in reducing the steady-state tracer content of the cells in the HCO3-buffered medium (22% versus 35% reduction), although the effects were similar in the initial phase of tracer uptake. Exposure to 10(-4) M 4-acetamido-4'-isothiocyanatostilbene-2,2'-disulphonic acid (SITS) caused an increase in the steady-state 36Cl content of the acini of 24 +/- 9%. Exposure to bumetanide and DIDS caused an additive reduction of tracer content, while exposure to bumetanide and SITS resulted in a smaller reduction than with bumetanide alone.(ABSTRACT TRUNCATED AT 250 WORDS)