Alteration of contractile and regulatory proteins in estrogen-induced hypertrophy of female rabbit bladder.
OBJECTIVE
Estrogen is essential to mediate physiologic functions in female bladders. Deficiency of estrogen has been speculated to be an etiologic factor for bladder dysfunction in postmenopausal women. Our previous studies have demonstrated that estrogen supplementation in female rabbits induces a "functional hypertrophy" of the urinary bladder smooth muscle. The present study investigated the alterations in the contractile and regulatory proteins in this model.


METHODS
Twenty New Zealand white female rabbits were separated into five groups of 4 rabbits each. Group 1 served as the control, groups 2 to 6 underwent ovariectomy (Ovx), and group 2 served as the Ovx without estradiol treatment group. Two weeks after Ovx, groups 3 to 5 were given 17-beta estradiol (1 mg/kg/day) by subcutaneous implant for 1, 3, and 7 days, respectively. The expression of the contractile and regulatory proteins, such as myosin light chain kinase, rho-kinase, and caldesmon, was analyzed by Western blotting.


RESULTS
The expression of myosin light chain kinase was enhanced by estradiol supplementation. The expression of rho-kinase-alpha was increased significantly (20-fold) after Ovx, which was downregulated after estrogen supplementation. No significant change was seen in rho-kinase-beta after Ovx or estradiol supplementation. The expression of caldesmon isoforms was enhanced by 1-day estradiol supplementation but decreased to lower levels than those of the control group by 3 and 7 days of estrogen treatment.


CONCLUSIONS
The results of the present study have provided more understanding about the role of the contractile and regulatory proteins in detrusor muscle, in both dysfunctional atrophy induced by Ovx and functional hypertrophy induced by estrogen supplementation.
Lin
Alpha Dian-Yu
AD
Albany College of Pharmacy, Albany, New York 12208, USA.
Levin
Robert M
RM
Kogan
Barry A
BA
Whitbeck
Catherine
C
Leggett
Robert E
RE
Kearns
Christine
C
Mannikarottu
Anita
A
D000818:Animals; D002148:Calmodulin-Binding Proteins / Q000096:biosynthesis* / Q000187:drug effects*; D003285:Contractile Proteins / Q000096:biosynthesis* / Q000187:drug effects*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D006984:Hypertrophy / Q000139:chemically induced; D047908:Intracellular Signaling Peptides and Proteins / Q000187:drug effects*; D009219:Myosin-Light-Chain Kinase / Q000096:biosynthesis* / Q000187:drug effects*; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000187:drug effects*; D011817:Rabbits; D001743:Urinary Bladder / Q000187:drug effects* / Q000473:pathology*; D054460:rho-Associated Kinases
D002148:Calmodulin-Binding Proteins; D003285:Contractile Proteins; D047908:Intracellular Signaling Peptides and Proteins; D004958:Estradiol; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D009219:Myosin-Light-Chain Kinase