Relationship between potency of L-isoprenaline and beta-adrenoceptor density estimated in single cells from tracheal smooth muscles of guinea pigs of different ages.
An age-related change in potency of L-isoprenaline in the presence of ascorbic acid, desmethylimipramine, corticosterone, pargyline, and phentolamine was obtained in tracheal strips from guinea pigs of differing ages between 6 and 40 weeks. The potency in the strips from 100-week-old guinea pigs did not significantly differ from that in strips from 40-week-old animals. Single cells were prepared from the tracheal muscles of 6-, 10-, 40-, and 100-week-old guinea pigs. The specific binding of [3H]dihydroalprenolol to the single cells was saturable. The dissociation constants of [3H]dihydroalprenolol were in good agreement with those of the membrane fractions from the guinea-pig tracheal muscles, and did not change with age. An excellent relationship between the potency of L-isoprenaline and the maximum binding of [3H]dihydroalprenolol estimated in the preparations from 6- to 40-week-old guinea pigs was found, suggesting that the increase in the potency of L-isoprenaline is due to the increase in the maximum binding or receptor density. The value in the preparations from 100-week-old guinea pigs deviated significantly from the regression line. This suggests the possibility that the decrease in potency in the strips from 100-week-old animals is due to a change in post beta-receptor processes in responsiveness.
Takayanagi
I
I
Department of Chemical Pharmacology, Toho University School of Pharmaceutical Sciences, Chiba, Japan.
Satoh
M
M
Kokubu
N
N
Kato
T
T
D000375:Aging / Q000502:physiology*; D000818:Animals; D001667:Binding, Competitive / Q000187:drug effects; D004082:Dihydroalprenolol; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009130:Muscle, Smooth / Q000166:cytology / Q000187:drug effects*; D011943:Receptors, Adrenergic, beta / Q000187:drug effects*; D014132:Trachea / Q000166:cytology / Q000187:drug effects
D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; D007545:Isoproterenol