Influence of age on epithelium-dependent responsiveness of guinea-pig and rat tracheal smooth muscle to spasmogens.
The current study describes the influence of age and the presence of the epithelium on guinea-pig and rat tracheal airway smooth muscle sensitivity to the spasmogens histamine, acetylcholine, carbachol and potassium. In guinea-pig trachea from animals aged 2-52 weeks the potency of each of these spasmogens decreased with increased animal age. In contrast, no age-dependent changes in the potency of acetylcholine, carbachol or potassium were seen in rat trachea. Removal of the tracheal epithelium was associated with significant increases in the potencies of histamine and acetylcholine in guinea-pig trachea and of acetylcholine in rat trachea, but not of carbachol or potassium in either species. For histamine in guinea-pig trachea, the largest potency increase (4.6-fold) occurred in tissue from 6-week-old animals, with the smallest increases in tissue from the youngest (2 weeks) and the oldest (52 weeks) animals. Thus, although the sensitivity of airway smooth muscle to this spasmogen fell between 2 and 12 weeks of age, the effect of epithelial removal on sensitivity to histamine was apparently increased during this period. Further studies are required to assess the reasons for increased histamine and acetylcholine potency in airway smooth muscle after epithelial ablation.
Preuss
J M
JM
Department of Pharmacology, University of Western Australia, Nedlands.
Henry
P J
PJ
Goldie
R G
RG
D000109:Acetylcholine / Q000494:pharmacology; D000375:Aging / Q000502:physiology*; D000704:Analysis of Variance; D000818:Animals; D002217:Carbachol / Q000494:pharmacology; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D006168:Guinea Pigs; D006632:Histamine / Q000494:pharmacology; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects*; D011188:Potassium / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D013035:Spasm / Q000503:physiopathology; D014132:Trachea / Q000187:drug effects* / Q000502:physiology
D006632:Histamine; D002217:Carbachol; D000109:Acetylcholine; D011188:Potassium