Protein kinase C and vascular smooth muscle contractility: effects of inhibitors and down-regulation.
We have compared two different methods of attenuating protein kinase C (PKC) activity in vascular smooth muscle. First, the effects of two purported PKC inhibitors, staurosporine (stauro) and H-7 [1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride], were examined on contractility of isolated, intact canine femoral artery. In arterial rings stauro was equipotent in relaxing contractions induced by phenylephrine (PE), phorbol-12,13-dibutyrate (PDBu) and KCl (IC50, 0.31 +/- 0.19; 0.35 +/- 0.2; and 0.34 +/- 0.16 microM). H-7, in comparison, was markedly less potent than stauro (IC50, 0.67 +/- 0.2, 2.33 +/- 0.24; and 6.5 +/- 5.5 microM for PE, PDBu and KCl, respectively). Pretreatment of tissues with 1 microM stauro suppressed tension development almost completely when PE and PDBu were the contractile agonists, and partially in K(+)-depolarized rings. H-7, in contrast, had no inhibitory effect on agonist-induced contraction. Neither basal nor K(+)-stimulated calcium influx was affected by 10 microM stauro. Second, prolonged exposure of canine carotid arterial rings to PDBu (1-100 nM for 24 hr), a means of depleting PKC from the tissue, caused dose-dependent attenuation of agonist-induced contractions. Preincubation with 100 nM PDBu caused complete inhibition of tension induced by norepinephrine (NE) and serotonin and partial inhibition of PDBu- and KCl-induced contractions. Lowering the concentration of PDBu during preincubation to 30, 10 or 1 nM reduced markedly the inhibitory effects. The inactive phorbolester 4 alpha-phorbol-12,13-didecanoate (4 alpha-PDD) had no effect on agonist-induced contractions. PKC activity was determined in rings contracted isometrically with PDBu or NE after prolonged exposure to vehicle, 4 alpha-PDD or PDBu.(ABSTRACT TRUNCATED AT 250 WORDS)
Merkel
L A
LA
Rhóne-Poulenc Rorer Central Research, King of Prussia, Pennsylvania.
Rivera
L M
LM
Colussi
D J
DJ
Perrone
M H
MH
D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D000470:Alkaloids / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism; D003864:Depression, Chemical; D004285:Dogs; D015536:Down-Regulation; D005260:Female; D066298:In Vitro Techniques; D007546:Isoquinolines / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000201:enzymology* / Q000502:physiology; D015240:Phorbol 12,13-Dibutyrate / Q000494:pharmacology; D010879:Piperazines / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D011493:Protein Kinase C / Q000032:analysis / Q000037:antagonists & inhibitors*; D019311:Staurosporine; D014661:Vasoconstriction / Q000187:drug effects*
D000470:Alkaloids; D007546:Isoquinolines; D010879:Piperazines; D015240:Phorbol 12,13-Dibutyrate; D019307:1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine; D011493:Protein Kinase C; D019311:Staurosporine; D011188:Potassium; D002118:Calcium