Effects of sensitization on the permeability of urothelium in guinea pig urinary bladder. 
Permeability of the guinea pig urinary bladder was investigated in a model of experimental cystitis induced by intravesical antigen challenge following sensitization.  Guinea pigs were sensitized by intraperitoneal injections of ovalbumin (10 mg./kg.)  given on days 1, 3, and 5.  The studies described were done four weeks after the last injection.  Controls (injected with saline) were used at the same time as sensitized animals.  Each group (control and sensitized), was divided into two subgroups; guinea pigs challenged with intravesical ovalbumin (10 mg./ml.,  one ml.)  and those receiving one ml.  saline intravesically.  Immediately following the antigen (or saline) challenge, one ml.  of 14C-urea urea was placed into the bladder for two hours.  We examined the peripheral blood concentrations of 14C-urea at periods of time up to 120 minutes.  There was a progressive increase in the blood level of 14C-urea with time only in the sensitized group challenged with antigen (ovalbumin).  There was no 14C-urea present in the blood of the sensitized group without antigen challenge, or in either unsensitized group.  We also measured isotope concentration in the bladders and found a significantly higher concentration of isotope in the bladders from ovalbumin-treated sensitized guinea pigs.  We believe that this animal model of cystitis is an improvement over previous models because of its physiological relevance.  In this model, cystitis is produced without mechanical or chemical damage to the bladder mucosa.  A discussion of the model in relation to interstitial cystitis is presented.