Effect of nitric oxide synthase inhibition on changes induced by estradiol in bladders from ovariectomized rabbits.
OBJECTIVE
Our current study was designed to determine whether estradiol-induced increases in bladder blood flow could be inhibited by N(omega)-nitro-L-arginine methyl ester (L-NAME), and thus whether nitric oxide was involved in estrogen-linked female bladder blood flow alterations.


METHODS
Sixteen female New Zealand White rabbits were separated into 4 groups of 4 rabbits each. (1) Sham group received sham operation and injections of vehicle (peanut oil). (2) Ovariectomy (OVX) group received ovariectomies and injections of vehicle. (3) Ovariectomy+estrogen (OVX+E) group received ovariectomy and injections of 17beta-estradiol (1 mg/kg) dissolved in peanut oil. (4) Ovariectomy+estradiol+L-NAME (OVX+E+L-NAME) group received ovariectomies and injections of 17beta-estradiol and L-NAME. All treatments were continued for 4 weeks. At 4 weeks after treatment, each rabbit was anesthetized and cystometries were performed. After cystometry, blood flow to the detrusor muscle and mucosa was determined by standard fluorescent microsphere infusion technique. Then four longitudinal detrusor strips and two rings of descending thoracic aorta were mounted in individual 15 ml baths containing oxygenated Tyrode's solution at 37 degrees C. Contractile responses to several agents were determined. Full-thickness sections of detrusor were fixed and embedded in paraffin for alpha-actin immunostaining.


RESULTS
In the bladder: (1) Estradiol resulted in an increases in bladder weight and blood flow; L-NAME inhibited these increases. (2) OVX resulted in a decreased cystometric capacity; estradiol resulted in increased capacity which was attenuated by L-NAME treatment. (3) OVX resulted in significantly decreased contractile responses to all forms of stimulation; estradiol resulted in significantly increased contractile responses which were attenuated by L-NAME treatment. (4) OVX resulted in a significant decrease in the volume-fraction of smooth muscle in the detrusor; estradiol resulted in a significant increase which was attenuated by L-NAME.


CONCLUSIONS
These findings strongly support the hypothesis that nitric oxide plays a major role in the alterations in blood flow mediated by changing circulating estrogen and that these changes mediate at least in part the cystometric and contractile changes induced by alterations in circulating estrogen.
Aikawa
Ken
K
Division of Basic and Pharmaceutical Sciences, Albany College of Pharmacy, Albany, NY 12208-3492, USA.
Chichester
Paul
P
Whitbeck
Catherine
C
Levin
Robert M
RM
D000704:Analysis of Variance; D000818:Animals; D001707:Biopsy, Needle; D003558:Cystoscopy; D004195:Disease Models, Animal; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D007150:Immunohistochemistry; D009119:Muscle Contraction / Q000187:drug effects* / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D019001:Nitric Oxide Synthase / Q000187:drug effects / Q000378:metabolism*; D010052:Ovariectomy; D011336:Probability; D011817:Rabbits; D011897:Random Allocation; D012016:Reference Values; D012039:Regional Blood Flow; D012307:Risk Factors; D012680:Sensitivity and Specificity; D001743:Urinary Bladder / Q000098:blood supply* / Q000187:drug effects / Q000473:pathology; D001745:Urinary Bladder Diseases / Q000473:pathology / Q000503:physiopathology; D014655:Vascular Resistance
D004958:Estradiol; D019001:Nitric Oxide Synthase; D019331:NG-Nitroarginine Methyl Ester