The effect of X irradiation on cardiac beta-adrenergic receptors in the rabbit.
Cardiac beta receptors in rabbits were studied at different times following lethal (5 Gy) or supralethal (10 Gy) whole-body X irradiation. Using the radioactive ligand [125I]iodocyanopindolol, it was found that the maximal binding capacity, as determined from the Scatchard plot, decreased from 298.2 +/- 13.2 fmole/mg protein in controls to 142.4 +/- 5.5 fmole/mg 3 days after 10 Gy whole-body X irradiation, whereas the dissociation constant was only little affected. Three days after an exposure to 5 Gy, maximal binding capacity was reduced slightly and tended toward control values at Day 7. Local irradiation of the cardiac region with 10 Gy reduced cardiac beta receptors to 218 +/- 7 fmole/mg (73% of control) after 3 days. The latter observation suggests that about half the effect of radiation on cardiac beta receptors originates from a direct action of radiation on the heart tissue, the rest being due to abscopal systemic reactions.
D000818:Animals; D006321:Heart / Q000294:innervation* / Q000528:radiation effects; D020120:Iodocyanopindolol; D008297:Male; D010869:Pindolol / Q000031:analogs & derivatives; D011817:Rabbits; D011869:Radioligand Assay; D011943:Receptors, Adrenergic, beta / Q000528:radiation effects*; D014916:Whole-Body Irradiation
D011943:Receptors, Adrenergic, beta; D020120:Iodocyanopindolol; D010869:Pindolol