hc-067047 and iberiotoxin

Kaempferol, a flavonoid, is the essential part of human diet. Flavonoids have different pharmacological activities like cardioprotective, anti-inflammatory and anti-oxidant. The aim of current study was to investigate vasorelaxant potential of kaempferol on rat isolated pulmonary artery and to assess the underling mechanisms.. Tension experiments were conducted on both the branches of main pulmonary artery of rats. Experiments were done using isolated organ bath system by recording tension with the help of data acquisition system, Power Lab.. Kaempferol (10. Kaempferol relaxes rat pulmonary artery in endothelium-independent manner through involvement of BK

Topics: Animals; Apamin; Barium Compounds; Calcium Chloride; Chlorides; Dose-Response Relationship, Drug; Endothelium, Vascular; Estradiol; Fulvestrant; Glyburide; In Vitro Techniques; Indomethacin; Isoquinolines; Kaempferols; Male; Morpholines; NG-Nitroarginine Methyl Ester; Oxadiazoles; Peptides; Potassium; Pulmonary Artery; Pyrroles; Quinoxalines; Rats; Sulfonamides; Tetraethylammonium; Vasodilation; Vasodilator Agents

We investigated the role of TRPV4 channels (TRPV4) in regulating the contractility of detrusor smooth muscle (DSM) and muscularis mucosae (MM) of the urinary bladder. Distribution of TRPV4 in DSM and MM of guinea-pig bladders was examined by fluorescence immunohistochemistry. Changes in the contractility of DSM and MM bundles were measured using isometric tension recording. Intracellular Ca(2+) dynamics were visualized by Cal-520 fluorescent Ca(2+) imaging, while membrane potential changes were recorded using intracellular microelectrode technique. DSM and MM expressed TRPV4 immunoreactivity. GSK1016790A (GSK, 1 nM), a TRPV4 agonist, evoked a sustained contraction in both DSM and MM associated with a cessation of spontaneous phasic contractions in a manner sensitive to HC-067047 (10 μM), a TRPV4 antagonist. Iberiotoxin (100 nM) and paxilline (1 μM), large conductance Ca(2+)-activated K(+) (BK) channel blockers restored the spontaneous contractions in GSK. The sustained contractions in DSM and MM were reduced by nifedipine (10 μM), a blocker of L-type voltage-dependent Ca(2+) channels (LVDCCs) by about 40 % and by nominally Ca(2+)-free solution by some 90 %. GSK (1 nM) abolished spontaneous Ca(2+) transients, increased basal Ca(2+) levels and also prevented spontaneous action potential discharge associated with DSM membrane hyperpolarization. In conclusion, Ca(2+) influx through TRPV4 appears to activate BK channels to suppress spontaneous contractions and thus a functional coupling of TRPV4 with BK channels may act as a self-limiting mechanism for bladder contractility during its storage phase. Despite the membrane hyperpolarization in GSK, Ca(2+) entry mainly through TRPV4 develops the tonic contraction.

Topics: Animals; Calcium Channel Blockers; Calcium Channels; Calcium Signaling; Guinea Pigs; Indoles; Large-Conductance Calcium-Activated Potassium Channels; Male; Morpholines; Muscle Contraction; Nifedipine; Peptides; Potassium Channel Blockers; Pyrroles; TRPV Cation Channels; Urinary Bladder