Increase in number of myocardial [3H]BAY K 8644 binding sites during adult maturation of rat.
In the present study we investigated the binding properties of [3H]BAY K 8644 to the purified sarcolemmal membrane, isolated from 2- and 12-month old Sprague-Dawley rats. Specific binding of [3H]BAY K 8644 was saturable and the Scatchard plot analysis revealed a single class of binding sites in purified sarcolemmal membrane. The estimated maximum number of binding sites in the membrane of 12-month-old rat was 2.4 +/- 0.1 pmol/mg protein, which was significantly greater than the maximum number of binding sites in 2-month-old rats (1.7 +/- 0.2 pmol/mg protein). The affinity to bind [3H]BAY K 8644 was, however, reduced in older rats (KD, 14.5 +/- 0.8 vs. 4.8 +/- 0.3 nM). Measurement of activities of sarcolemmal and subcellular marker enzymes showed that the purification of membrane was virtually identical in two age groups. This would suggest that membrane purity was not a contributing factor to the observed increase in [3H]BAY K 8644 receptor density. Since dihydropyridine receptor sites are very likely to represent voltage-gated calcium channels of sarcolemma, it is concluded that the density of myocardial voltage-gated calcium channels increases during adult maturation.
Department of Medicine, University of Manitoba, Winnipeg, Canada.
S
S
Navaratnam
J C
JC
Khatter
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000378:metabolism*; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002118:Calcium / Q000494:pharmacology; D015220:Calcium Channels / Q000378:metabolism; D007700:Kinetics; D008297:Male; D008566:Membranes / Q000187:drug effects / Q000201:enzymology; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D011978:Receptors, Nicotinic / Q000378:metabolism; D012519:Sarcoplasmic Reticulum / Q000187:drug effects / Q000378:metabolism; D013347:Subcellular Fractions / Q000187:drug effects / Q000201:enzymology
D015220:Calcium Channels; D011978:Receptors, Nicotinic; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D002118:Calcium