['Compliance is primarily related to extracellular matrix deposition, and prolyl 4-hydroxylase (P4Hs) plays a critical role in the synthesis of the matrix. To study the alteration of P4Hs, under the influence of variable hydrostatic pressure, a novel pressure device was used to expose human bladder smooth muscle cells (HBSMC) and fibroblasts (HBF) to pressures in the physiologic range. We then studied acute obstructed porcine bladder tissues to see if changes can also be seen after in-vitro obstruction.', 'HBSMC and HBF were exposed to pressures at 0, 20 and 40 cmH(2)O for up to 72 h. In-vivo studies were carried out next, using six normal (control) and five obstructed porcine bladders. Pigs were exposed to a consistent hydrostatic pressure of < or =20 cm for 24 h after ligation of the urethra. We used 2-DE to compare protein profiling of HBSMC under normal and increased pressures. Other analyses were used to detect molecular alteration and altered expression of mRNA for P4Hs.', 'We identified 437 proteins from 476 spots (91.8%) obtained from HBSMC that were differentially expressed under normal and increased pressures. Under increased pressure, 48 unique proteins were significantly increased or decreased, and a prominent protein regulating extracellular matrix synthesis highly correlated with P4Hs. The exposure of both HBSMC and HBF to a sustained hydrostatic pressure resulted in the increased expression of P4Hs in a time- and pressure-dependent manner. In vivo, P4Hs expression was also significantly increased in the obstructed group.'] Is collagen prolyl 4-hydroxylase up-regulated in an acute bladder outlet obstruction?