['Previous studies have shown that there is a time-dependent upregulation of contractile endothelin B (ETB) receptors in middle cerebral arteries (MCA) after organ culture. This upregulation is dependent on mitogen-activated protein kinases and possibly protein kinase C (PKC). The aim of this study was to examine the effect of PKC inhibitors with different profiles on the upregulation of contractile ETB receptors in rat MCA. Artery segments were incubated for 24 hours at 37 degrees C. To investigate involvement of PKC, inhibitors were added to the medium before incubation. The contractile endothelin-mediated responses were measured and real-time PCR was used to detect endothelin receptor mRNA levels. Furthermore, immunohistochemistry was used to demonstrate the ETB receptor protein distribution in the MCA and Western blot to measure which of the PKC subtypes that were affected by the inhibitors.', 'The PKC inhibitors bisindolylmaleimide I, Ro-32-0432 and PKC inhibitor 20-28 attenuated the ETB receptor mediated contractions. Furthermore, Ro-32-0432 and bisindolylmaleimide I decreased ETB receptor mRNA levels while PKC inhibitor 20-28 reduced the amount of receptor protein on smooth muscle cells. PKC inhibitor 20-28 also decreased the protein levels of the five PKC subtypes studied (alpha, betaI, gamma, delta and epsilon).'] Does inhibition of PKC activity block the increase of ETB receptor expression in cerebral arteries?