Author/Editor		Hernandez, DE; Walker, CH; Valenzuela, JE; Mason, GA
Title		Biochemical identification of dopamine binding sites in human gastric muscle
Type		članek
Source		Exp Clin Gastroenterol
Vol. and No.		Letnik 1, št. 1
Publication year		1991
Volume		str. 61-4
Language		eng
Abstract		Evidence indicates that exogenous dopamine affects gastric motility in humans; however, the molecular basis for the motility effects of dopamine are currently undetermined. Radioligand binding studies were performed with increasing concentrations of 3H-dopamine (50-200 nM) on crude memebrane fractions prepared from human gastric muscle obtained from six patients. The assay was performed in triplicate at 22 degrees C for 30 min in the dark and terminated by vacuum filtration. The extent of non-specific binding (30 per cent) was determined by addition of a 100-fold excess of unlabeled dopamine to the incubation mixture. Analysis of the binding data revealed that 3H-dopamine binding was saturable and receptor density (Bmax) was estimated at 250+-85 pmol/mg protein. The equilibrium dissociation constant (Kd) obtained from the regression line of the Scatchard plot was 5.4+-0.7 nM. Finally, the Hill coefficient (nH) was estimated at 1.1, suggesting a lack of interaction or cooperativity among binding sites. These biochemical findings contribute to explain the effects of exogenously-administered dopamine on gastric motility. Characterization of this binding domain may provide critical insight into the molecular mechanisms of dopamine neurotransmission in gastric smooth muscle cells
Descriptors		RECEPTORS, DOPAMINE MUSCLE, SMOOTH STOMACH BINDING SITES GASTROINTESTINAL MOTILITY DOPAMINE