Oxidative stress disruption of receptor-mediated calcium signaling mechanisms

Table 1 Influence of tBHP on [ ³ H]MS binding to human muscarinic receptors expressed in CHO cells

Receptor subtype	Treatment	K_D, nM	[Receptor], pmol/mg protein	k₋₁(min^-1)	k₋₁(min^-1), with gallamine
M3	Control	0.39 ± 0.07	2.1 ± 0.2	0.014 ± 0.002	0.009 ± 0.003
M3	tBHP	0.49 ± 0.10	1.9 ± 0.2	0.015 ± 0.003	0.010 ± 0.002
M2	Control			0.027 ± 0.004	0.004 ± 0.001
M2	tBHP			0.021 ± 0.006	0.005 ± 0.002

[³H]MS binding was measured in untreated cells (Control) or in cells exposed to 2 mM tBHP for 90 min before harvesting the cells for binding measurements.
K_D, equilibrium dissociation constant; [Receptor], receptor density; k₋₁ rate constant for [³H]MS dissociation.
Mean ± S.D. (N = 3). None of the parameters measured after exposure to tBHP were significantly different from the corresponding control value. Gallamine decreased the dissociation rate constants (p < 0.05 with M3 receptors; p < 0.01 with M2 receptors); dissociation rate constants were not altered in cells exposed to 2 mM tBHP.

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