GROWTH RESISTANCE-SIZED ARTERIES IN RESPONSE TO BLADDER HYPERTROPHY IN THE RAT - TIME-COURSE, DNA-SYNTHESIS AND LDH-ISOFORM PATTERN

Bladder growth was induced by partial urethral obstruction. Bladder hy pertrophy was evident at 53 h after obstruction and continued over a 6 weeks period, Small bladder arteries were taken from fixed anatomical locations of the bladder circulation. mounted in a small vessel myogr aph and the optimal diameter for maximal isometric force development w as determined (L(max), K+ = 125 mM stimulation). Bladder hypertrophy w as associated with an enlarged L(max) from 53 h onward (compared with sham-operated controls) and L(max) continued to increase until 10 days after urethral obstruction. Between 10 days and 6 weeks no further in crease of the diameter was observed. Increased diameters in vitro were accompanied by a transiently increased [H-3]Thymidine uptake in the s mall arteries which peaked al 53 h after obstruction but was still abo ve background at 10 days. At this time point. small arterial growth wa s associated with a significant relative increase in the M isoform of LDH as determined with agarose electrophoresis on tissue homogenates. Thus organ growth induced small vessel growth in the rat is characteri zed by a rapid onset, increased but transient DNA-turnover and LDH-iso form changes. The latter mimic changes seen in other types of smooth m uscle growth.