0000000000882501
AUTHOR
J.m. Vila
Endothelium-independent contractions of human cerebral arteries in response to vasopressin.
We studied the effects of vasopressin in isolated segments from branches (500-700 micrograms in external diameter) of human middle cerebral arteries obtained during autopsy of 15 patients who had died 3-8 hours before. Paired segments, one normal and the other de-endothelized by gentle rubbing, were mounted for isometric recording of tension in organ baths. In 11 normal segments, vasopressin produced concentration-dependent contractions with an EC50 of 7.0 X 10(-10) M. Removal of the endothelium from 12 segments did not significantly affect vasopressin-induced contractions. Vasopressin produced further contractions in arterial segments with (n = 4) or without (n = 5) endothelium precontract…
Role of endothelium and calcium channels in endothelin-induced contraction of human cerebral arteries
Endothelin constricted human isolated cerebral arteries in a concentration-dependent manner. The maximal tension developed, as well as EC50 values were similar in arteries with and without endothelium. Removal of extracellular calcium or addition of the calcium antagonist nicardipine (10(-6)M), attenuated but did not abolish responses to endothelin. These experiments show that the endothelin-induced contraction in human cerebral arteries is not linked to the presence of intact endothelial cells. The data also show that the contractile effects of endothelin cannot be explained solely by an action on voltage-dependent calcium channels.
Contractile Response of Human Omental Arteries to Endothelin
Abstract The effects of endothelin have been studied in isolated arterial segments (0·8–1 mm in external diam.) of human omental arteries obtained during the course of abdominal operations (15 patients, 7 men and 8 women). Paired segments, one normal and the other de-endothelized, were mounted for isometric recording of tension in organ baths. Endothelin produced concentration-dependent contractions with an EC50 value of 5·4 × 10−9 m. Removal of endothelium did not affect significantly endothelin-induced contractions (EC50, 6·7 × 10−9 m). Removal of extracellular calcium or addition of the calcium channel blocker nicardipine (10−6 m) diminished but did not abolish responses to endothelin…
NG-monomethyl-L-arginine and NG-nitro-L-arginine inhibit endothelium-dependent relaxations in human isolated omental arteries.
Abstract The L-arginine analogues NG-monomethyl-l-arginine (l-NMMA, 10−4 m) and NG-nitro-L-arginine methyl ester (l-NAME, 10−4 m), which specifically inhibit the synthesis of nitric oxide from l-arginine, significantly reduced acetylcholine-induced endothelium-dependent relaxations in rings of human omental arteries. The inhibitory potency of l-NMMA and l-NAME was similar. Addition of l-NMMA or l-NAME to the organ bath did not induce any significant changes in the resting tension of the tissues. The effects of l-NMMA were reversed by l-arginine (3 × 10−4 m). The l-NMMA enantiomer, d-NMMA (10−4 m), did not influence either the basal tone of the preparation or the relaxing effects of acet…