Detection of muscarinic receptor subtypes in human urinary bladder mucosa: Age and gender-dependent modifications

Aims: Muscarinic receptor subtypes expressed in the human urinary bladder mucosa were characterized, investigating whether there were gender-dependent differences and if aging could induce changes in their expression. Methods: The study was carried out on 34 subjects, 22 men and 12 women, divided in four groups, based on gender and age. Gene expression was evaluated by quantitative RT-PCR. The Western blot was performed using the 4–12% NuPAGE Bis–Tris Gel System. Results: The molecular expression of each subtype of the M1 receptor family was observed and it was not influenced either by gender or age. M2 receptor family transcripts revealed that both M2 and M4 were detected and that the M2 transcripts were modified by both gender and age. Indeed, M2 mRNA was lower in old rather than adult men (P < 0.05), but higher in rather old than adult women (P < 0.05). Further, adult men expressed more M2 mRNA than adult women (P < 0.05), while the opposite was detected in old age (P < 0.05). The Western blot followed by quantification confirmed that the mRNAs were translated into proteins, and that the M2 subtype showed similar modifications found at molecular level. Discussion: The selective modification of M2 receptors observed at the urinary bladder mucosa levels indicates that this anatomical structure could play an active role in the pathophysiology of micturition and supports evidence suggesting an effect of antimuscarinic drugs at this level. Whether these results may influence the age-dependent development of micturition disorders remains to be determined.