Download The Calcium-Release-Activated Calcium Channels Role in

The Calcium-Release-Activated Calcium Channels Role in Contractile Response of Isolated
Human Urinary Bladder Smooth Muscle
Introduction and Objectives: Urine continence is dependent on urinary bladder (UB) ability to store
urine at low pressure (by active relaxation of detrusor) and mechanism resulting in urethral pressure
higher than urine pressure in UB. At the cellular level, these processes are strongly associated with
cytoplasmic calcium levels ([Ca2+]IC). Increases of [Ca2+]IC occur primarily as a result of extracellular
Ca2+ entry through plasma membrane ion channels and release of Ca2+ from the endoplasmic
reticulum (ER). Except for voltage-gated channels, the Ca2+ metabolism is dependent on storeoperated channels (SOCs) activity. The morphological studies confirmed presence of more SOCs on
UB smooth muscle (SM), e.g. TRP channels, and their involvement in UBSM was evidenced.
Recently, TRPC4 channels and calcium-release-activated calcium channels (CRAC) role is discussed
as possible mechanisms in urine incontinence pathogenesis. CRAC, Ca2+-high selective ion channels,
consist of Ca2+ sensor - protein STIM1 located on ER and plasma membrane protein Orai1. The
mutation of STIM1 protein leads to persistent accumulation and permanent activation of CRAC.
Materials and Methods: Presented study was aimed on investigation of relationship between CRAC
and contraction/relaxation mechanisms of UBSM by pharmacological method. All experiments were
approved by Ethics Committee of the Jessenius Faculty of Medicine (decision No. EK 611/2010).
Human UBSM samples were collected from 14 men during radical prostatectomy according to well
defined criteria. Carbachol (10-5 M/l) initially precontracted-tissue strips (10x3x5 mm) contractile
response to cumulative doses of CRAC inhibitor (3-fluoropyridine-4-carboxylic acid, c=10-6-10-3 M/l)
and control drug oxybutinin (c=10-6-10-3 M/l) were tested by tissue bath method. The occurrence of
CRAC on UBSM cells was analyzed immunohistochemically (using anti-Orai1 antibody).
Results: CRAC antagonist significantly (p≤0.05 and p≤0.01) and dose-dependently decreased
contractile amplitude of UBSM strips in comparison to initial carbachol-induced contraction. This
response was similar to oxybutinin-induced UBSM relaxation. Immunohistochemical staining
visualized CRAC as mild or middle membrane positivity.
Conclusion: The results confirmed significant role of CRAC in UBSM cells contraction mediated by
parasympathetic nervous system. According to effectiveness of CRAC antagonist similar to
oxybutinin, the knowledge resulting from the study may possibly influence pharmacotherapy of
diseases accompanied by the pathological changes of UBSM contractility.