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Ontogenic aspects of D 1 receptor coupling to G proteins and regulation of rat jejunal Na + , K + ATPase activity and electrolyte transport
Author(s) -
VieiraCoelho M A,
SoaresdaSilva P
Publication year - 2000
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 - 10.1038/sj.bjp.0703065
Subject(s) - chemistry , biophysics , membrane transport , receptor , ion transporter , electrolyte , coupling (piping) , endocrinology , biology , biochemistry , membrane , materials science , electrode , metallurgy
The present study examined the effect of dopamine on rat jejunal electrolyte transport (rheogenic transport and Na + , K + ‐ATPase activity) in adult (60‐day old) and young (20‐day old) animals. In young rats, dopamine, in the presence of phentolamine, produced an increase in jejunal I sc , this being completely abolished by SKF 83566, and not changed by S‐sulpiride. SKF 38393, but not quinerolane, also increased I sc ; this effect was abolished by SKF 83566 and ouabain, but not by furosemide. In adult rats, dopamine in the presence of phentolamine (0.2 μ M ) decreased I sc . Na + , K + ‐ATPase activity in isolated jejunal epithelial cells from adult rats was 2.4 fold that in young rats. In the presence of phentolamine, both dopamine and SKF 38393, but not quinerolane, significantly decreased jejunal Na + , K + ‐ATPase activity in young animals but not in adult animals. Binding [ 3 H]‐Sch 23390 to membranes of jejunal mucosa revealed the presence of a single class of receptors in both young and adult rats, with similar K D and B max values. GTPγS and cholera toxin inhibited jejunal Na + , K + ‐ATPase activity in young, but not in adult rats. Co‐incubation of pertussis toxin with dopamine was found to potentiate the inhibitory effects of dopamine upon the enzyme in both young and adult rats. Regulation of Na + , K + ‐ATPase activity by cholera toxin‐sensitive G proteins is absent in adult animals, and such difference may explain the failure of dopamine to inhibit intestinal Na + , K + ‐ATPase activity in adult rats.British Journal of Pharmacology (2000) 129 , 573–581; doi: 10.1038/sj.bjp.0703065