Spinal cord injury (SCI) at Th13 was induced in female Wistar rats, an
d changes in the urinary bladder were examined during the acute phase
of SCI. Wet weights of the spinal bladders increased twofold over cont
rols by 7 days after SCI. Intravesical volumes increased sixfold over
control values by day 3, and then decreased 7 days after the injury. M
aximal pressure within the bladder decreased in all spinal rats compar
ed with controls. Smooth muscle cells were isolated from the urinary b
ladder, and their total protein and DNA content were measured by multi
parametric cytofluorometry. DNA content of isolated smooth muscle cell
s decreased by day 3 and remained 7 days after the spinal injury. Tota
l protein content of isolated smooth muscle cells was decreased 1 day
after and increased 7 days after the spinal injury, just when spinal r
eflex of the bladder recovered. These findings suggest that hypertroph
y of smooth muscle cells in urinary bladder is related to the activity
of peripheral autonomic nerve and that smooth muscle cells already be
gin to hypertrophy during the spinal shock period to adjust themselves
to the new state, that is, the spinal bladder.