Reduced alpha 1-adrenergic receptor-mediated inositide hydrolysis in cardiac atria of senescent rats.
We investigated the effect of age on epinephrine stimulation of phosphoinositide hydrolysis in atrial slices prepared from F-344 female rats. Three age groups were chosen for study: young adults (aged 6 months), mature adults (aged 15 months), and senescent animals (aged 25 months). Tissue slices were labeled with [3H]myoinositol and epinephrine-stimulated hydrolysis measured in the presence of LiCl. Epinephrine caused a dose-dependent increase in phosphoinositide hydrolysis in each age group. This increase was blocked by prazosin, suggesting that alpha 1-adrenergic receptors are involved. In animals aged 6 months, epinephrine caused a maximal increase in hydrolysis of 2.8-fold over basal. The maximal response was reduced at 15 months (2.52-fold increase, p less than 0.05) and at 25 months (2.02-fold increase, p less than 0.01). The potency for epinephrine stimulation of phosphoinositide hydrolysis was unchanged with age. The data indicate that alpha 1-mediated phosphoinositide hydrolysis in atria is reduced with age.
Geriatric Research, Education and Clinical Center, VA Medical Center, Gainesville, FL 32602.
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Borst
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Narang
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Crews
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PJ
Scarpace
D000375:Aging / Q000378:metabolism*; D000818:Animals; D004837:Epinephrine / Q000494:pharmacology; D005260:Female; D006325:Heart Atria; D006868:Hydrolysis; D066298:In Vitro Techniques; D007292:Inosine Nucleotides / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D011224:Prazosin / Q000494:pharmacology; D051381:Rats; D011916:Rats, Inbred F344; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*
D007292:Inosine Nucleotides; D011942:Receptors, Adrenergic, alpha; D011224:Prazosin; D004837:Epinephrine