Effects of stress and chronic propranolol infusion on cardiac beta-receptor function in the Maudsley Reactive and Non-Reactive rat strains.
The effects of beta-adrenoceptor blockade on left ventricular beta-receptor characteristics were evaluated in the Maudsley Reactive (MR/Har) and Non-Reactive (MNRA/Har) rat strains. After propranolol infusion for one week administered by subcutaneously implanted osmotic minipumps, differences in beta-adrenoceptor-agonist interactions between strains were assessed by comparison of isoproterenol competition for [125I]iodocyanopindolol (ICYP) binding sites in crude left ventricular homogenate preparations from both strains. Propranolol exposure had no significant effect on the binding parameters investigated (Bmax, Kd, % receptors in high affinity state, IC50). In contrast to previous observations in naive animals, these experiments revealed no strain differences in the sham-implanted Maudsleys in any of the left ventricular beta-adrenoceptor parameters investigated. We hypothesize that the surgical procedures and/or presence of the plastic inserts acted as stressors in the Maudsley strains and thus altered beta-adrenoceptor function. This hypothesis is supported by the observation that exposure to another stress (footshock) also eliminated strain differences in ventricular beta-receptor binding variables.
Christ
G J
GJ
Department of Physiology and Pharmacology, Bowman Gray School of Medicine, Wake Forest University, Winston-Salem, NC 27103.
Pieper
J A
JA
Blizard
D A
DA
Dunlap
C E
CE
D000818:Animals; D001667:Binding, Competitive; D004326:Drinking / Q000187:drug effects; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D007457:Iodine Radioisotopes; D020120:Iodocyanopindolol; D007545:Isoproterenol / Q000378:metabolism / Q000494:pharmacology; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010869:Pindolol / Q000031:analogs & derivatives / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology*; D051381:Rats; D011922:Rats, Mutant Strains; D011943:Receptors, Adrenergic, beta / Q000187:drug effects / Q000378:metabolism*; D013045:Species Specificity; D013312:Stress, Physiological / Q000378:metabolism*
D007457:Iodine Radioisotopes; D011943:Receptors, Adrenergic, beta; D006165:Guanylyl Imidodiphosphate; D020120:Iodocyanopindolol; D011433:Propranolol; D010869:Pindolol; D007545:Isoproterenol