Protein synthesis and rapid recovery of endothelium-dependent dilation after endothelial injury of pial arterioles

A laser-dye technique is known to injure selectively microvascular endothelium in situ. With the use of the arterioles on the surface of the mouse brain (pial arterioles), the endothelial injury is manifest by loss of several endothelium- dependent responses, including the dilation produced by topical application of acetylcholine (ACh), bradykinin (BK), and calcium ionophore A-23187. The responses normally recover by 60 min following injury. The present study shows that inhibitors of protein synthesis prevent the recovery. Either actinomycin D (Act-D; 1 mg/kg) or cycloheximide (CX; 10 mg/kg) was injected intraperitoneally 35 min before the light-dye injury. The CX was used in separate studies with ACh, BK, and ionophore. In each study, recovery of the endothelium-dependent dilation failed to occur 60 min after injury, while recovery occurred in contemporary vehicle-treated controls. Act-D was used in separate studies of ACh and BK. Again, recovery of endothelium-dependent dilation was prevented. Neither CX nor Act-D inhibited the response to ACh in uninjured vessels. Thus response to ACh was intact in such arterioles 90 min after the injection of CX or Act-D. CX was also given to uninjured mice and was found to have no inhibitory action on the response to ionophore 90 min later. CX and Act-D inhibit protein synthesis by very different mechanisms, inhibition of translation and of transcription, respectively. Because both prevented recovery of the endothelium-dependent responses, we conclude that one or more rapidly synthesized proteins are required for the recovery.