Decrease in bladder overactivity with REN1820 in rats with cyclophosphamide induced cystitis.

PURPOSE: Studies suggest that nerve growth factor (NGF) contributes to bladder overactivity stemming from bladder inflammation. Studies were performed to determine the NGF dependence of cyclophosphamide (CYP) induced changes in bladder function using the recombinant NGF sequestering protein REN1820. MATERIALS AND METHODS: Urodynamic testing and behavioral observations were made in female rats treated with CYP (4 or 48 hours) and REN1820 or vehicle. RESULTS: Rats examined 4 or 48 hours after CYP treatment plus REN1820 showed significantly fewer nonvoiding contractions with smaller amplitude (p

Cyclophosphamide induced cystitis alters neurotrophin and receptor tyrosine kinase expression in pelvic ganglia and bladder.

PURPOSE: We examined neurotrophin and receptor tyrosine kinase (Trk) expression in the bladder and major pelvic ganglia (MPG) after cyclophosphamide induced cystitis in rats. MATERIALS AND METHODS: The bladder and MPG were used in immunohistochemical studies, enzyme-linked immunoassays and Western blots for nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), TrkA and TrkB. Bladder postganglionic MPG cells were labeled by tracing techniques. RESULTS: NGF and BDNF expression was decreased in the bladder of all rats after cystitis (p < or =0.001). NGF and BDNF expression was increased in the MPG in male rats with cystitis (p < or =0.01). Cells expressing TrkA and TrkB immunoreactivity (IR) increased 78% to 81% in the MPG in male rats with cystitis. TrkA-IR or TrkB-IR bladder postganglionic cells increased 50% to 74% with cystitis. Cystitis increased TrkA-IR 5 to 10-fold and TrkB-IR 10 to 12-fold in detrusor muscle. TrkA-IR and TrkB-IR were prominent in control urothelium but decreased with cystitis. After cystitis TrkB-IR nerve fibers and TrkA-IR cellular infiltrates were more apparent compared to controls. CONCLUSIONS: Cystitis decreases bladder NGF and BDNF expression, whereas MPG expression is increased. This change may reflect neurotrophin release at the bladder and retrograde transport to the MPG. TrkA-IR and TrkB-IR are increased in bladder postganglionic cells and bladders with cystitis. This increase may reflect a shift in Trk staining from urothelium to detrusor muscle and nerve fibers with cystitis. Neurotrophin/Trk interactions in the bladder and MPG may contribute to bladder overactivity with cystitis.

A mechanogated nonselective cation channel in proximal tubule that is ATP sensitive.

Ion channels that are gated in response to membrane deformation or "stretch" are empirically designated stretch-activated channels. Here we describe a stretch-activated nonselective cation channel in the basolateral membrane (BLM) of the proximal tubule (PT) that is nucleotide sensitive. Single channels were studied in cell-intact and cell-free patches from the BLM of PT cells that maintain their epithelial polarity. The limiting inward Cs+ conductance is ~28 pS, and channel activity persists after excision into a Ca2+- and ATP-free bath. The stretch-dose response is sigmoidal, with half-maximal activation of about -19 mmHg at -40 mV, and the channel is activated by depolarization. The inward conductance sequence is: NH ~ Cs+ ~ Rb+ > K+ ~ Na+ ~ Li+ > Ca2+ ~ Ba2+ > N-methyl-D-glucamine ~ tetraethylammonium. The venom of the common Chilean tarantula, Grammostola spatulata, completely blocks channel activity in cell-attached patches. Hypotonic swelling reversibly activates the channel. Intracellular ATP concentration ([ATP]i) reversibly blocks the channel (inhibitory constant approximately 0.48 mM), suggesting that channel function is coupled to the metabolic state of the cell. We conclude that this channel may function as a Ca2+ entry pathway and/or be involved in regulation of cell volume. We speculate this channel may be important when [ATP]i is depleted, as occurs during periods of increased transepithelial transport or with ischemic injury.