Abstract

Dimethyl sulfoxide (DMSO) is a dipolar organic compound commonly used as a solvent in studies of membrane transport. DMSO also has many effects on cell function and, although the precise mechanism of action is not known completely, it has been stated to exert its effect on transport solely through osmolality. The present study was designed to examine the effects of serosal DMSO at three osmolar concentrations on Basal Water Flow and vasopressin (AVP)- and cyclic AMP-stimulated water flow (Maximal Water Flow) in the toad bladder. The results obtained were compared to equi-osmolar concentrations of mannitol and NaCl. All three agents significantly enhanced Basal Water Flow after 60 min. The results obtained on Maximal Water Flow were different depending on the final osmolality. At 300 mOsm final concentration, all three agents increased AVP-stimulated water flow. When the serosal osmolality was 600 or 900 mOsm DMSO increased Maximal Water Flow, whereas mannitol and NaCl decreased it. When 300 mOsm DMSO plus 300 mOsm mannitol (600 mOsm total)-treated hemibladders were challenged with AVP, the water flow response was similar to that of 600 mOsm DMSO alone. In the presence of verapamil, AVP-stimulated water flow was decreased markedly; when DMSO was added to verapamil-pretreated hemibladders, and they were then challenged with AVP, water flow increased significantly. In similar experiments with mannitol, water flow remained inhibited. Dimethylsulfone did not enhance AVP-stimulated water flow as compared to the same concentration of DMSO. These results demonstrate that the effects of DMSO on water transport are not mediated solely by its osmolar action.(ABSTRACT TRUNCATED AT 250 WORDS)