Transient receptor potential channels in rat renal microcirculation: actions of angiotensin II.
BACKGROUND
This study assessed the calcium-activating mechanisms mediating glomerular arteriolar constriction by angiotensin II (Ang II).


METHODS
Immunohistochemical and physiological studies were carried out, using antibody against transient receptor potential (TRP)-1 and an isolated perfused kidney model.


RESULTS
Immunohistochemical experiments demonstrated that TRP-1 proteins were transcribed on both afferent and efferent arteriolar myocytes. In the first series of physiological experiments, Ang II (0.3 nmol/L) considerably constricted afferent (20.2 +/- 0.9 to 14.9 +/- 0.7 microm) and efferent arterioles (18.4 +/- 0.7 to 14.0 +/- 0.7 microm). The addition of nifedipine (1 micromol/L) restored decrements in afferent (to 20.0 +/- 0.8 microm) but not efferent arteriolar diameters. Further administration of SKF-96365 (100 micromol/L), a TRP channel blocker, reversed efferent arteriolar constriction (to 16.2 +/- 0.8 micromol/L). In the second group, although 2-aminoethoxydiphenyl borate (100 micromol/L), an inhibitor of inositol trisphosphate-induced calcium release (IP3CR), did not alter glomerular arteriolar diameters, it prevented Ang II-induced afferent arteriolar constriction and attenuated efferent arteriolar constriction (18.8 +/- 0.8 to 16.9 +/- microm). Subsequent removal of extracellular calcium abolished residual efferent arteriolar constriction (to 19.1 +/- 0.8 microm).


CONCLUSIONS
Our data provide evidence that Ang II elicits IP3CR, possibly inducing a cellular response that activates voltage-dependent calcium channels on afferent arterioles. The present results suggest that Ang II-induced efferent arteriolar constriction involves IP3CR and calcium influx sensitive to SKF-96365.
Department of Medicine, Saitama Medical College, Saitama, Japan.
Tsuneo
T
Takenaka
Hiromichi
H
Suzuki
Hirokazu
H
Okada
Tsutomu
T
Inoue
Yoshihiko
Y
Kanno
Yuri
Y
Ozawa
Koichi
K
Hayashi
Takao
T
Saruta
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D001160:Arterioles / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000502:physiology; D007093:Imidazoles / Q000494:pharmacology; D015640:Ion Channel Gating / Q000187:drug effects / Q000502:physiology; D007678:Kidney Glomerulus / Q000098:blood supply; D009543:Nifedipine / Q000494:pharmacology; D051381:Rats; D017207:Rats, Sprague-Dawley; D012079:Renal Circulation / Q000187:drug effects* / Q000502:physiology*; D012433:Ryanodine / Q000494:pharmacology; D050052:TRPC Cation Channels; D014662:Vasoconstrictor Agents / Q000494:pharmacology*
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D007093:Imidazoles; D050052:TRPC Cation Channels; D014662:Vasoconstrictor Agents; C096351:transient receptor potential cation channel, subfamily C, member 1; D000804:Angiotensin II; D012433:Ryanodine; C063159:1-(2-(3-(4-methoxyphenyl)propoxy)-4-methoxyphenylethyl)-1H-imidazole; D009543:Nifedipine; D002118:Calcium