Influence of age on the rhythm in basal and forskolin-stimulated adenylate cyclase activity of the rat heart.
In male rats of three different ages (Group I: 7 weeks, Group II: 4 months, Group III: greater than 10 months) basal and forskolin-stimulated adenylate cyclase (AC) activity were investigated in rat heart ventricles of animals sacrificed at 8 time points within 24 hours of a day. Maximum (Emax) and half-maximum (EC50) stimulation by a water-soluble forskolin (FOR; 0.1-100 mumol/l) were determined from dose-response curves. In young rats (Group I) significant rhythmicity was found in basal and FOR-stimulated AC activity, which was successively reduced or abolished with age by a reduction in amplitude. Mean basal AC activity increased about 2-fold from Group I to Group II/III. Mean maximum in FOR stimulation was about 12-fold in Group I and about 7-fold in Group II and III. EC50-values displayed neither a significant rhythmicity in either group nor an age-dependency. It is concluded that the stimulatory potency of the catalytic subunit of the AC is reduced with age.
Lemmer
B
B
Zentrum der Pharmakologie, J.W. Goethe-Universität, Frankfurt/M, F.R.G.
Wald
C
C
D000262:Adenylyl Cyclases / Q000378:metabolism*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D002940:Circadian Rhythm / Q000502:physiology*; D005576:Colforsin / Q000494:pharmacology; D006352:Heart Ventricles / Q000201:enzymology; D008297:Male; D009206:Myocardium / Q000201:enzymology*; D051381:Rats; D011919:Rats, Inbred Strains
D005576:Colforsin; D000262:Adenylyl Cyclases