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  • Title: Diphenylhydantoin inhibition of drug-induced contractions of isolated rat vas deferens: additional evidence for a calcium-blocking action.
    Author: Calixto JB, De-Lima TC.
    Journal: Braz J Med Biol Res; 1983 Dec; 16(4):327-31. PubMed ID: 6673812.
    Abstract:
    The present study analyzed the inhibitory effects of diphenylhydantoin (DPH) on acetylcholine (Ach)-, norepinephrine (NE)- and 5-hydroxytryptamine (5-HT)-induced contractions of the isolated rat vas deferens in normal bath medium. The effect of DPH on CaCl2-induced contractions of depolarized preparations was also investigated. Pre-incubation with 30 microM to 1mM DPH for 20 min promoted a non-competitive antagonism of Ach-, 5-HT- and NE-induced contractions with pD'2 values of 4.0 +/- 0.11, 4.05 +/- 0.10 and 3.38 +/- 0.10, respectively. In contrast, 12.5 microM to 100 microM DPH caused parallel, dose-related, rightward displacements of the dose-response curve to CaCl2 in potassium depolarizing solution. The Schild plot of these data was linear and compatible with a competitive antagonism by DPH of Ca2+-induced contractions (pA2 = 4.75 +/- 0.2; slope = 0.99). These results strongly suggest that, in the isolated rat vas deferens, DPH interferes competitively with Ca2+ membrane translocation, thus inhibiting the action of several neurotransmitters in a non-competitive manner.
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