Mast Cell Accumulation and Degranulation in Rat Bladder with Partial Outlet Obstruction.
BACKGROUND
Benign prostatic hyperplasia causes partial bladder outlet obstruction (pBOO), and many patients with pBOO are affected by not only voiding symptoms but also storage symptoms. We previously suggested that enhancement of 5-hydroxytryptamine (5-HT)-induced bladder contraction in the pBOO bladder may be one cause of storage symptoms. However, little is known about the presence of 5-HT in rat bladders. In this study, we hypothesized that mast cells are a source of 5-HT and investigated the distribution of mast cells and 5-HT in the bladders of rats with pBOO.


METHODS
The bladders of female Sprague-Dawley rats were subjected to pBOO and sham operations for 1 week, were isolated, and were fixed for light or electron microscopy. Mast cells and 5-HT in the bladders were detected by toluidine blue staining and immunohistochemical staining, respectively. The mast cells were counted under a light microscope. Degranulated mast cells were observed under an electron microscope and counted under a light microscope.


RESULTS
Mast cells were present in the mucosa/submucosa region in sham rat bladders. Their number was increased in the detrusor muscle/subserosa/serosa region, especially the subserosal layer, in pBOO rat bladders. The localization of mast cells almost matched that of 5-HT-positive cells in consecutive sections. Degranulated mast cells were present in sham and pBOO rat bladders, but the proportion of degranulated mast cells was significantly increased in every region in pBOO rat bladders compared with that in sham rat bladders.


CONCLUSIONS
These results suggest that mast cells contain 5-HT and are more abundant locally in the subserosal layer of pBOO rat bladders. 5-HT released from mast cells could stimulate 5-HT2 receptors on the detrusor muscle, and this may underlie storage symptoms.


BACKGROUND
Asahi Kasei Pharma Corp.
Laboratory for Pharmacology, Pharmaceuticals Research Center, Asahi Kasei Pharma Corporation, 632-1, Mifuku, Izunokuni-shi, Shizuoka, 410-2321, Japan.
Mai
M
Michishita
Laboratory for Pharmacology, Pharmaceuticals Research Center, Asahi Kasei Pharma Corporation, 632-1, Mifuku, Izunokuni-shi, Shizuoka, 410-2321, Japan.
Ken-Ichi
K
Tomita
Laboratory for Pharmacology, Pharmaceuticals Research Center, Asahi Kasei Pharma Corporation, 632-1, Mifuku, Izunokuni-shi, Shizuoka, 410-2321, Japan.
Kazuo
K
Yano
Laboratory for Pharmacology, Pharmaceuticals Research Center, Asahi Kasei Pharma Corporation, 632-1, Mifuku, Izunokuni-shi, Shizuoka, 410-2321, Japan. kasahara.kc@om.asahi-kasei.co.jp.
Ken-Ichi
K
Kasahara
D000818:Animals; D015550:Cell Degranulation; D004195:Disease Models, Animal; D005260:Female; D007150:Immunohistochemistry; D059411:Lower Urinary Tract Symptoms / Q000175:diagnosis*; D008407:Mast Cells / Q000502:physiology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D001743:Urinary Bladder / Q000473:pathology*; D001748:Urinary Bladder Neck Obstruction / Q000209:etiology / Q000473:pathology / Q000503:physiopathology
5-Hydroxytryptamine; Benign prostatic hyperplasia; Bladder outlet obstruction; Degranulation; Distribution; Mast cell; Rat; Subserosa