Platelet alpha-adrenoceptor function and aging.
The effect of aging on platelet alpha-adrenoceptor binding of 3H-dihydro-alpha-ergocryptine (3H-DHE) and alpha-adrenoceptor response expressed as cAMP decrease, after the addition of noradrenaline 10 microM to intact platelets in vitro were examined and correlated with adrenaline induced platelet aggregation in a group of twelve young volunteers (mean age 21 years), and twelve old volunteers (mean age 88 years). The binding by platelets of 3H-DHE was considerably higher in the young than in the old group (mean 292.70 +/- 40.79 and 167.90 +/- 18.30 fmol/mg protein respectively, p less than 0.02). The affinity (Kd) was also influenced with values of 1.49 +/- 0.21 in the young and 3.32 +/- 0.45 nM in the old, p less than 0.01). Stimulation of platelets with noradrenaline caused a greater decrement of cAMP in the old than in the young group (mean 4.44 +/- 0.87 as compared with 0.32 +/- 0.75 pmol/10(9) platelets. Platelet sensitivity to adrenaline, when expressed as aggregation increased in the old group. These data suggest that the enhanced sensitivity to adrenaline as observed in old people is not the result of increased alpha-adrenoreceptor number of affinity, but related to changes in the platelet membrane possibly not related to the alpha-adrenoceptors.
Winther
K
K
Naesh
O
O
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000502:physiology*; D001792:Blood Platelets / Q000502:physiology / Q000648:ultrastructure*; D000242:Cyclic AMP / Q000032:analysis / Q000378:metabolism; D004088:Dihydroergotoxine / Q000378:metabolism; D006801:Humans; D009638:Norepinephrine / Q000494:pharmacology; D010974:Platelet Aggregation / Q000187:drug effects; D011485:Protein Binding; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000032:analysis / Q000502:physiology*
D011942:Receptors, Adrenergic, alpha; D004088:Dihydroergotoxine; D000242:Cyclic AMP; D009638:Norepinephrine