title: Adverse effects of artificial buffers on contractile responses of arterial and venous smooth muscle.
abstract: 1 In vitro studies were undertaken on rat aortic strips and portal vein segments in order to determine whether or not several commonly used artificial buffers, i.e., tris(hydroxymethyl) aminomethane (Tris), N-2-hydroxyethylpiperazine-N'-2-ethanesulphonic acid (HEPES), morpholine propanesulphonic acid (MOPS), N,N bis(2-hydroxyethyl) glycine (BICINE) and 1,4-piperazinediethanesulphonic acid (PIPES), can exert direct actions on vascular smooth muscle. 2 All artificial buffers used in 5 mM concentrations were found to inhibit development of spontaneous mechanical activity. 3 Tris, HEPES, MOPS, BICINE and PIPES markedly attenuated contractions induced by adrenaline, angiotensin and KCl. The fast phase components of the agonist-induced contractions were either obliterated or reduced in the presence of the artificial buffers. The sustained slow phase components were greatly reduced and retarded by the artificial buffers. 4 The relative order of artificial buffer potency (i.e., from 100% to 14% inhibition) seems to depend upon the agonist and type of smooth muscle. 5 All of these inhibitory effects were reversible, since normal contractile responses and spontaneous mechanical activity could be obtained by simply reincubating the smooth muscles in Krebs-Ringer bicarbonate buffer. 6 A variety of pharmacological antagonists failed to mimic or affect the inhibitory effects of Tris, HEPES, MOPS, PIPES and BICINE. 7 These data show that five of the most commonly used artificial buffers, to study muscles in vitro, exert adverse effects on contractility of arterial and venous smooth muscle.
mesh_terms: D000476:Alkanesulfonates / Q000494:pharmacology; D000804:Angiotensin II / Q000494:pharmacology; D000818:Animals; D002021:Buffers; D002118:Calcium / Q000378:metabolism; D004837:Epinephrine / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives* / Q000494:pharmacology; D006531:HEPES / Q000494:pharmacology*; D066298:In Vitro Techniques; D008297:Male; D009025:Morpholines / Q000494:pharmacology*; D009119:Muscle Contraction / Q000187:drug effects*; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D010879:Piperazines / Q000494:pharmacology*; D011189:Potassium Chloride / Q000494:pharmacology; D051381:Rats; D014325:Tromethamine / Q000494:pharmacology*
chemical_list: D000476:Alkanesulfonates; D002021:Buffers; D009025:Morpholines; D010879:Piperazines; D014325:Tromethamine; D000804:Angiotensin II; C027494:N,N-bis(2-hydroxyethyl)glycine; C008550:morpholinopropane sulfonic acid; D011189:Potassium Chloride; D006531:HEPES; D002118:Calcium; D005998:Glycine; D004837:Epinephrine