Effects of aging on AV nodal and ventricular β-adrenergic receptors in the Fischer 344 rat

F. M. Kusumoto, K. G. Lurie, J. Dutton, H. Capili, J. B. Schwartz

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Abstract

The effects of aging on atrioventricular (AV) nodal and right and left ventricular β-adrenergic receptor (β-AR) characteristics were studied in Fischer 344 rat hearts using quantitative autoradiography. Twenty-micrometer- thick cardiac sections containing the compact AV node from 16 mature (4-6 mo old) rats, 6 middle-aged (12 mo old) rats, and 16 old (24 mo old) rats were incubated with [125I]iodocyanopindolol, [125I]iodocyanopindolol plus atenolol, or ICI 118551. Saturation experiments revealed a significant age- related decrease in AV nodal β-AR density (mature: 190 ± 46, middle-aged: 165 ± 27, old: 133 ± 34 amol/mm2; P < 0.01), with no change in affinity (mature: 106 ± 62, middle-aged: 132 ± 46, old: 128 ± 66 pM). No age- related changes in AV nodal β-AR subtype ratio (55% β1, 45% β2) or estimated compact AV node volume were detected (mature: 66 ± 17, old: 65 ± 23 μm3). No difference in β-AR density or affinity was detected between mature and old rats in either left (LV) or right (RV) ventricular tissue (LV, mature: 60 ± 11, middle-aged: 59 ± 11, old: 62 ± 11 amol/mm2; RV, mature: 65 ± 9, middle-aged: 65 ± 11, old: 58 ± 10 amol/mm2). β-AR subtype ratios for the left ventricle (64% β1, 36% β2) and right ventricle (63% β1, 37% β2) did not significantly differ between mature and old rats. To summarize, aging from 4 to 24 mo in the Fischer 344 rat is associated with 1) a decrease in AV nodal β-AR density with no change in affinity; 2) no change in volume of the compact region of the AV node; 3) no change in β-AR subtype ratio in the AV node, left ventricle, or right ventricle; and 4) no change in either RV or LV β-AR density.

Original languageEnglish (US)
Pages (from-to)H1408-H1415
JournalAmerican Journal of Physiology - Heart and Circulatory Physiology
Volume266
Issue number4 35-4
StatePublished - 1994

Keywords

  • atrioventricular node volume
  • autoradiography
  • β-adrenergic receptor subtype

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