Abstract
Summary
The purpose of this study was to gain insight into the role of sulfhydryl (SH) groups in arterial receptors for vasoactive simulants. We studied the effects of p-chloromercuriphenyl sulfonate (PCMBS, 10-6 to 10-4 M), a potent and specific SH binding agent, on contractile responses produced with 10-5 M epinephrine and 10-5 M serotonin in helical strips of arterial smooth muscle prepared from tail arteries of the rat. Responses to epinephrine were rapidly, markedly, and reversibly inhibited with low concentrations of PCMBS. In contrast, responses to serotonin were slowly inhibited when high concentrations of PCMBS were tested. The inhibitory effect of PCMBS (10-5 M) on epinephrine-induced contractions was prevented by 10-3 M cysteine. Alpha-adrenergic blockade with phentol-amine (10-4 or 5 × 10-6 M) virtually abolished responses to epinephrine and significantly decreased responses to serotonin. These findings are consistent with the view that arterial receptors for contractile responses to epinephrine and serotonin may be structurally related. The data suggest that SH groups are important functional components of adrenergic receptors, but that they are of lesser importance for responsiveness of serotonin receptors.
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