Bladder Surface Glycosaminoglycans: An Epithelial Permeability Barrier

Abstract

Sulfated polysaccharide''s ability to modulate the movement of small molecules was examined both in vivo and in vitro. For the in vivo test, the rabbit bladder was utilized and C-14 labeled urea 45-Ca, or 3H2O was placed into the lumen of control bladders, bladders pretreated with protamine sulfate (20 mg./cc) and bladders pretreated with protamine sulfate (20 mg./cc) and bladders pretreated with protamine sulfate (20 mg./cc) plus pentosanpolysulfate (PPS), 10 mg./cc. After 45 minutes, the controls absorbed 21% of the urea, 16% of the calcium, and 38% of the 3H2O; the protamine treated group 40% urea, 23% calcium, and 51% H2O; the PPS only group 22% urea and the protamine plus PPS group absorbed 24% of urea, 18% calcium, and 44% water. Differences between the control and protamine groups were statistically significant, p < 0.01 for urea 45-Ca and 3H2O. The bladder mucosa contained a significantly higher concentration of urea and calcium after protamine treatment which were both reversed by PPS (p < 0.01) while 3H2O content went down significantly (p = 0.03), reflecting a loss of the hydrophilic effect of bladder GAG. The control mucosas has 250 cpm/mg. tissue urea for a Ca 64 cpm/mg. and water 262 cpm/mg., the protamine group urea 498 cpm/mg., Ca 190 cpm/mg., and H2O 139 cpm/mg.; the protamine plus PPS group urea 344 cpm/mg., ca 129 cpm/mg., and water 168 cpm/mg. For the in vitro studies, an Ussing chamber was employed. Normal rabbit bladder membranes were placed in the chambers and the potential differences was zeroed across the membrane. There were three groups, membranes that were treated only with the irrigating solution, membranes pretreated with protamine, and membranes pretreated with protamine plus PPS. At the end of 40 minutes, there was an approximately 1.2% movement of urea across the control membrane, a 3.5% movement across the protamine treated membrane (a significant increase p < 0.001) and a 1.1% movement across the protamine plus PPS treated membrane. It would appear that the surface polysacchardie may play an important role as a bladder permeability barrier in modulating both charged and uncharged small molecule movement in that its ability to impair such movements can be inhibited by protamine and this protamine effect can be reversed by a treatment with an exogenous sulfated polysaccharide.