Selective potentiation of histamine H1-receptor stimulated calcium responses by 1,4-dithiothreitol in DDT1MF-2 cells.
The effect of 1,4-dithiothreitol (DTT) on agonist-stimulated increases in intracellular free calcium concentration ([Ca2+]i) has been investigated in the smooth muscle cell line, DDT1MF-2, derived from hamster vas deferens. Pretreatment with DTT (1 mM) produced a large leftward parallel shift in concentration-response curve for histamine H1-receptor mediated increases in [Ca2+]i. The EC50 values for H1-receptor stimulated increases in [Ca2+]i in the absence and presence of DTT were 11.3 +/- 1.5 microM (N = 6) and 0.52 +/- 0.15 microM (N = 6), respectively. DTT had no significant effect on the maximum Ca2+ response elicited by histamine (100 microM). In the presence of DTT the partial H1-receptor agonist 2-pyridylethylamine (100 microM) increased [Ca2+]i from 112 +/- 14 nM to 237 +/- 24 nM (N = 10). In control cells 2-pyridylethylamine (100 microM) did not elicit a Ca2+ response. DTT had no significant effect on the maximum Ca2+ response elicited by 1 mM 2-pyridylethylamine. The enhancement of histamine H1-receptor Ca2+ responses by DTT was reversed by the sulphydryl oxidizing agent dithiobis-(2-nitrobenzoic acid). DTT had no significant effect on adenosine A1-, bradykinin and ATP-receptor stimulated increases in [Ca2+]i. [3H]mepyramine binding experiments confirmed that DTT increased agonist affinity. DTT produced a small, but significant, leftward shift in concentration-response curve for histamine displacement of [3H]mepyramine binding. These data suggest that DTT potentiates H1-receptor mediated Ca2+ responses by increasing agonist affinity.
Department of Physiology and Pharmacology, Medical School, Queen's Medical Centre, Nottingham, U.K.
J M
JM
Dickenson
S J
SJ
Hill
D000241:Adenosine / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D001920:Bradykinin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D006224:Cricetinae; D004229:Dithiothreitol / Q000494:pharmacology*; D004357:Drug Synergism; D006632:Histamine / Q000494:pharmacology; D008297:Male; D009130:Muscle, Smooth / Q000187:drug effects / Q000378:metabolism; D011738:Pyrilamine / Q000494:pharmacology; D011969:Receptors, Histamine H1 / Q000187:drug effects* / Q000378:metabolism
D011969:Receptors, Histamine H1; C048599:N(6)-cyclopentyladenosine; D006632:Histamine; D011738:Pyrilamine; D000241:Adenosine; D001920:Bradykinin; D002118:Calcium; D004229:Dithiothreitol