Muscarinic receptor transcript and protein density in hypertrophied and atrophied rat urinary bladder.
OBJECTIVE
Our previous studies showed that bladder hypertrophy shifts the muscarinic receptor subtype mediating contraction from M(3) towards M(2) along with increased M(2) and decreased M(3) protein concentration. We quantified mRNA for M(1) through M(5) receptors to determine whether the changes in M(2) and M(3) protein levels was due to changes in transcription.


METHODS
Bladder hypertrophy was induced by bladder outlet obstruction (BOO), major pelvic ganglion electrocautery (DEN), and major pelvic ganglion decentralization (DEC). Bladder atrophy was induced by ureteral diversion (DIV). Additional groups included denervated and diverted (DEN-DIV), sham operated (SHAM), and normal (NOR) controls. Transcripts were quantified using a multiplex ribonuclease protection assay (RPA) and receptor protein density was determined by immunoprecipitation. Receptor transcripts were expressed per unit total RNA.


RESULTS
Although all five receptor subtype transcripts were detected in all experimental groups, the densities of M(1), M(4), and M(5) were much lower than for the M(2) and M(3) subtype. There were more M(2) receptor transcripts than all the others, consistent with M(2) protein determinations. M(2) transcripts were significantly increased in DEN and BOO bladders. Surprisingly, M(3) transcripts were also significantly increased in BOO. There was a significant correlation (r=0.98, P<0.001) between protein density and transcript density for the M(2) but not the M(3) receptor among the different experimental groups.


CONCLUSIONS
Changes in mRNA concentration are reflected by changes in protein density for the M(2) receptor but not for the M(3) receptor. Extrapolation of functional effects from transcript density data is invalid for M(3) mediated bladder contractions.
Braverman
Alan S
AS
Department of Urology, Temple University School of Medicine, Philadelphia, Pennsylvania 19140, USA.
Ruggieri
Michael R
MR
D000818:Animals; D001284:Atrophy; D003714:Denervation; D005260:Female; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases / Q000235:genetics; D006984:Hypertrophy; D023282:Nuclease Protection Assays; D011506:Proteins / Q000378:metabolism; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D051381:Rats; D017207:Rats, Sprague-Dawley; D011976:Receptors, Muscarinic / Q000235:genetics*; D012269:Ribosomal Proteins / Q000235:genetics; D001743:Urinary Bladder / Q000378:metabolism* / Q000473:pathology; D001748:Urinary Bladder Neck Obstruction / Q000473:pathology; D014547:Urinary Diversion
D011506:Proteins; D012333:RNA, Messenger; D011976:Receptors, Muscarinic; D012269:Ribosomal Proteins; C041806:ribosomal protein L32; D005987:Glyceraldehyde-3-Phosphate Dehydrogenases