Functional substance P receptors on a human astrocytoma cell line (U-373 MG)

Abstract

[ 125I]Bolton Hunter conjugate of substance P ([ 125I]BHSP) can bind to human astrocytoma membranes in a monophasic and saturable manner with a K dof0.57 ± 0.17nM and a B maxof67.8 ± 5.5fmol/mg protein. The rank order of potency of tachykinins and related analogues as inhibitors of [ 125I]BHSP binding to astrocytoma membranes and intact cells correlated with their relative abilities to stimulate uridine incorporation into nucleic acid. The observed specificity pattern conformed to that reported for the NK1 tachykinin receptor withSP≫eledoisin>neurokinin A>neurokinin B and[Glp 6, l-Pro 9]SP(6–11)≫[Glp 6, d-Pro 9]SP(6–11).