The detrusor muscle of the bladder shows abundant expression of the ?2-adrenoreceptor (ADRB2), and polymorphisms of the ADRB2 gene have been suggested to show a close association with various allergic disorders. Nishijima and associates from the University of Ryukyus in Okinawa and the National Sagamihara Hospital in Kawagawa, Japan examined the relationship between the response of PBS/IC to tricyclic antidepressant therapy and polymorphism of the ADRB2 (arg16Gly) gene.

The authors studied 55 IC patients and 113 controls. The IC patients were treated with imipramine hydrochloride, and the efficacy of treatment was assessed to be no change, fair, or good. They then analyzed ADRB2 genotypes and showed a significant difference in the prevalence of the Arg16Gly polymorphism between IC patients and controls. Arg/Arg was associated with a 3.66-fold increase in the risk of IC compared with Arg/Gly or Gly/Gly.

Regarding the relationship between the Arg16Gly polymorphism and the efficacy of tricyclic antidepressant therapy, a significant difference of Arg16Gly polymorphism prevalence was observed between IC patients with no change or a fair response to tricyclic treatment and the controls. There was no such difference between IC patients with a good response to tricyclic treatment and the controls. In patients with IC, Arg/Arg was associated with a 2.97-fold decrease of the response rate to tricyclic antidepressant therapy compared with Arg/Gly or Gly/Gly.

The authors suggest that Arg/16Gly polymorphism of ADRB2 is related to the down-regulation of ADRB2 expression by the detrusor muscle of the bladder, and that the effect of tricyclic antidepressant therapy on IC depends on ADRB2 genotype. One can only speculate that the differences noted may have been even more striking if amitriptyline had been used in place of imipramine.

Saori Nishijima, Kimio Sugaya, Tetsuo Yamada, Minoru Miyazato and Yoshihide Ogawa

Biomedical Research, Vol. 27, pp.163-167 (2006)

Written by Philip M. Hanno, MD, a Contributing Editor with UroToday.

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