Molecular heterogeneity of leukotriene receptors: correlation of smooth muscle contraction and radioligand binding in guinea-pig lung.
The [3H]leukotriene C4 ([3H]LTC4) and [3H]leukotriene D4 ([3H] LTD4) specific binding sites in guinea-pig lung membranes were characterized and correlated with smooth muscle contractile activities of a series of LTC-, D- and E-type analogs. [3H]LTC4 bound to the specific sites with high affinity (dissociation constant Kd = 15 +/- 5 nM), saturable capacity (maximum binding = 68 +/- 15 pmol/mg of membrane protein), stereoselectivity and specificity. The [3H]LTC4 specific binding sites were detected in the membranes isolated from leukotriene sensitive (e.g., lung and heart) or insensitive (e.g., brain and red blood cells) tissues. [3H] LTD4 also bound to specific sites with high affinity (Kd = 0.20 +/- 0.05 nM), low capacity (maximum binding = 1.1 +/- 0.2 pmol/mg of membrane protein) stereoselectivity and specificity. The [3H] LTD4 specific binding sites were detected in the membranes isolated from lung and trachea. [3H]LTC4 specific binding was inhibited by treatment of the membranes with the sulfhydryl alkylating agent N-ethylmaleimide. [3H]LTD4 specific binding was more sensitive to heat treatment and p-hydroxymercuribenzoate than the [3H]LTC4 specific binding. Radioligand competition activities of the LTD- and LTE-type analogs correlated well with the agonist and antagonist smooth muscle contractile activities. In contrast, the radioligand competition activity of the LTC-type analogs did not correlate with smooth muscle contractile activities. These results indicate that the [3H]LTC4 and [3H]LTD4 specific binding sites in guinea-pig lung membranes are chemically and physically distinct. The [3H]LTD4 specific binding sites represent physiologically and pharmacologically important receptors, and the smooth muscle contraction induced by LTD-, and possible LTE-, type analogs are mediated through the LTD4 receptors.
Mong
S
S
Wu
H L
HL
Scott
M O
MO
Lewis
M A
MA
Clark
M A
MA
Weichman
B M
BM
Kinzig
C M
CM
Gleason
J G
JG
Crooke
S T
ST
D000818:Animals; D001667:Binding, Competitive; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology; D005033:Ethylmaleimide / Q000494:pharmacology; D006168:Guinea Pigs; D006358:Hot Temperature; D006902:Hydroxymercuribenzoates / Q000494:pharmacology; D066298:In Vitro Techniques; D008168:Lung / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects*; D009130:Muscle, Smooth / Q000187:drug effects*; D011869:Radioligand Assay; D011956:Receptors, Cell Surface / Q000032:analysis*; D018077:Receptors, Leukotriene; D011982:Receptors, Prostaglandin / Q000032:analysis*; D013189:SRS-A / Q000378:metabolism / Q000494:pharmacology*; D014132:Trachea / Q000187:drug effects
D006902:Hydroxymercuribenzoates; D011956:Receptors, Cell Surface; D018077:Receptors, Leukotriene; D011982:Receptors, Prostaglandin; D013189:SRS-A; C030601:4-hydroxymercuribenzoate; D004024:Dicyclohexylcarbodiimide; D005033:Ethylmaleimide