Improved contractility of obstructed bladders after Tadenan treatment is associated with reversal of altered myosin isoform expression

Purpose: Tadenan is a plant extract from Pygeum fricanum used in the treatm ent of benign prostatic hyperplasia, to protect the bladder from contractil e dysfunction induced by partial bladder outlet obstruction (BOO). The aim of the present study was to determine whether the Tadenan-induced return of detrusor contractility affects the expression of myosin isoforms, which di ffer at the C-terminal (SM1 and SM2) and the N-terminal regions (SM-A and S M-B). Materials and Methods: Four groups of New Zealand White rabbits (3 to 5 kg. , 4 to 6 rabbits per group) were either partially obstructed by ligation of the urethra (groups 1 and 2) or not obstructed (groups 3 and 4). After 2 w eeks, rabbits from groups 2 and 4 received Tadenan in peanut oil (vehicle) orally at 100 mg./kg./day for 3 weeks and rabbits in groups 1 and 3 receive d vehicle only. Rabbits were sacrificed and bladders were removed and weigh ed. Contractility studies were performed on isolated strips of detrusor and the remaining muscular layer from the bladder body was used to study the e xpression of myosin heavy chain (MHC) isoforms at mRNA (SM1, SM2, SM-A, and SM-B) and the protein (SM1 and SM2) levels by RT-PCR and SDS-PAGE analyses , respectively. Results: Tadenan significantly reduced the effect of BOO on bladder mass. T he diminished contractile response to field stimulation and carbachol secon dary to urethral obstruction was significantly reversed by Tadenan treatmen t. The relative ratios for MHC isoforms were altered at the mRNA (SM2:SM1 a nd SM-A:SM-B) and protein (SM2:SM1) levels in obstruction. Upon treatment w ith Tadenan, the ratio of these isoforms returned to normal, as shown at. t he mRNA levels. In addition, the altered relative ratio of SM2:SM1 at the p rotein level also returned to nearly normal values after treatment. Conclusions: Improvement of obstruction-induced contractile dysfunction of the detrusor following treatment with Tadenan is associated with changes in the expression of myosin isoforms. The alteration in the expression of myo sin isoforms associated with obstruction-induced hypertrophy is reversed cl ose to normal in the detrusor smooth muscle from Tadenan-treated obstructed rabbits.