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CARDIAC β‐ADRENOCEPTORS DURING NORMAL GROWTH OF MALE AND FEMALE RATS
Author(s) -
BAKER STEPHEN P.,
POTTER LINCOLN T.
Publication year - 1980
Publication title -
british journal of pharmacology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.432
H-Index - 211
eISSN - 1476-5381
pISSN - 0007-1188
DOI - 10.1111/j.1476-5381.1980.tb10699.x
Subject(s) - receptor , endocrinology , medicine , dihydroalprenolol , sarcolemma , dissociation constant , adrenergic receptor , biology , cell surface receptor , myocyte , agonist , partial agonist
1 A binding assay involving (−)‐[ 3 H]dihydroalprenolol (DHA) and KCl‐washed cardiac membranes was used to assess the numbers and affinities of β‐adrenoceptors in hearts from male and female rats varying in age from about 2 weeks to 18 months. 2 Although female rats grow more slowly and attain lower adult weights than male rats, heart weights increased in approximate proportion to body weight with little sex difference. 3 As heart weight increased about three fold, β‐receptors increased three fold. Since the number of myocardial cells is believed to be nearly constant during postnatal growth, the numbers of receptors/cell presumably increases similarly. 4 As heart weight increased, the number of β‐receptors per g of tissue decreased according to the equation: total pmol/g = 4.33 − 1.43 × heart weight, equally in males and females. 5 Dissociation constants for DHA (2 to 4 n m ) remained the same, and equal, in male and female rats during their growth. 6 An excellent correlation was found between the decline in β‐receptors/g tissue during growth and the decline in the area of the external sarcolemma/g tissue. The data suggest that the number of receptors per unit area remains constant during growth, and thus that cell surface area is a major factor determining normal numbers of receptors per cardiocyte.