Role of protein kinase C in angiotensin II-induced constriction of renal microvessels.
Role of protein kinase C in angiotensin II-induced constriction of renal microvessels.


BACKGROUND
Although angiotensin II (Ang II) exerts its action through multiple vasomotor mechanisms, the contribution of phosphoinositol hydrolysis products to Ang II-induced renal vasoconstriction remains undetermined.


METHODS
The role of protein kinase C (PKC) in Ang II-induced afferent (AFF) and efferent (EFF) arteriolar constriction was examined using the isolated perfused hydronephrotic rat kidney.


RESULTS
Ang II (0.3 nmol/L)-induced EFF constriction was refractory to inhibition of voltage-dependent calcium channels by pranidipine (1 micromol/L, 19 +/- 2% reversal) but was completely reversed by a PKC inhibitor, chelerythrine (1 micromol/L, 96 +/- 2% reversal). Furthermore, direct PKC activation by phorbol myristate acetate (PMA; 1 micromol/L) caused prominent EFF constriction, and this constriction was inhibited by manganese and free calcium medium. In contrast, Ang II-induced AFF constriction was completely abolished by pranidipine (98 +/- 4% reversal) and was partially inhibited by chelerythrine (55 +/- 3% reversal). Although PMA elicited marked AFF constriction, this constriction was insensitive to the calcium antagonist, but was totally inhibited by manganese or free calcium medium.


CONCLUSIONS
PKC plays an obligatory role in Ang II-induced EFF constriction that requires extracellular calcium entry through nonselective cation channels. In contrast, in concert with our recent findings demonstrating a complete dilation by thapsigargin, Ang II-induced AFF constriction is mainly mediated by inositol trisphosphate (IP3) and voltage-dependent calcium channel pathways, but could not be attributed to the PKC-activated calcium entry pathway (for example, nonselective cation channels). Rather, Ang II-stimulated PKC may cross-talk to the IP3/voltage-dependent calcium channel pathway and could modulate the vasoconstrictor mechanism of the AFF. Thus, the role of PKC during Ang II stimulation differs in AFF and EFF, which may constitute segmental heterogeneity in the renal microvasculature.
Nagahama
T
T
Department of Internal Medicine, School of Medicine, Keio University, Tokyo, Japan.
Hayashi
K
K
Ozawa
Y
Y
Takenaka
T
T
Saruta
T
T
D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D015220:Calcium Channels / Q000378:metabolism; D004789:Enzyme Activation; D015640:Ion Channel Gating; D007668:Kidney / Q000098:blood supply* / Q000187:drug effects; D008297:Male; D011493:Protein Kinase C / Q000378:metabolism*; D051381:Rats; D011921:Rats, Inbred WKY; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D010738:Type C Phospholipases / Q000378:metabolism; D014661:Vasoconstriction / Q000187:drug effects*
D015220:Calcium Channels; D000804:Angiotensin II; D011493:Protein Kinase C; D010738:Type C Phospholipases; D013755:Tetradecanoylphorbol Acetate; D002118:Calcium