Characteristics of endothelin receptors in the cerebral cortex and spinal cord of aged rats.
Characteristics of endothelin receptors were studied in male Fischer 344 rats at 4-, 15- and 24-months of age and [125I]ET-1 binding showed a single high affinity binding site in their cerebral cortex and spinal cord membranes. The density and affinity of ET binding sites were found to be similar in rats of various age groups. To determine the affinity of ET isotypes to ET-1 binding sites in cerebral cortex and spinal cord, competition studies were performed and K(i) values of ET-1, ET-2 and ET-3 for [125I] ET-1 binding sites were determined. It was found that ET-1 had 100 and ET-2 had 25-100 times lower K(i) values as compared to ET-3, indicating that ET receptors in cerebral cortex and spinal cord are of ETA type. In spinal cord, the K(i) values of ET-1 and ET-2 for ET receptor were found to be similar. However, in cerebral cortex the K(i) values of ET-1 were found to be at least 6 times lower than ET-2. It is inferred that there are two subtypes of ET(A) receptors, ET(A1) which have higher affinity for ET-1 in comparison to ET-2, as found in cerebral cortex and ET(A2) which have higher affinity for ET-2, as found in spinal cord. The K(i) and IC50 values of ET-1, ET-2, and ET-3 for [125I]ET-1 binding sites in cerebral cortex and spinal cord were found to be similar in 4-, 15- and 24-month-old rats.(ABSTRACT TRUNCATED AT 250 WORDS)
Bertelsen
G A
GA
Department of Pharmacodynamics, University of Illinois, Chicago 60612.
Rebello
S
S
Gulati
A
A
D000375:Aging / Q000378:metabolism*; D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000378:metabolism; D051381:Rats; D011916:Rats, Inbred F344; D011956:Receptors, Cell Surface / Q000502:physiology*; D017466:Receptors, Endothelin; D013116:Spinal Cord / Q000378:metabolism*; D014757:Viper Venoms / Q000378:metabolism
D011956:Receptors, Cell Surface; D017466:Receptors, Endothelin; D014757:Viper Venoms; C057354:sarafotoxins s6