The effects of transmitters on the affinity of the insoluble fraction of Ox brain for Na⁺ and K⁺

Abstract

The insoluble fraction of ox-brain, which had previously been shown to have a non-linear affinity for Na⁺ and K⁺, was prepared. Acetylcholine (1×10⁻⁸ mol/l and 1×10⁻⁷ mol/l) reduced the affinity of the fraction for Na⁺ and K⁺ to zero, while at 1×10⁻⁶ mol/l, the affinity for the cations was almost as high as in the absence of the transmitter; the affinities for Na⁺ and K⁺ were particularly high, when the supernatant concentrations of these ions exceeded 80–100 mM. Addition of eserine (3×10⁻⁵ mol/l) considerably modified the response of the fraction to acetylcholine (1×10⁻⁵ mol/l). Atropine (1×10⁻⁸ mol/l) in the absence or presence of acetylcholine (1×10⁻⁵, or 1×10⁻⁴ mol/l) reduced the affinity of the fraction for Na⁺ and K⁺ to zero. Epinephrine (3×10⁻¹⁰ mol/l) lowered the affinity for Na⁺ and K⁺, while ergotamine itself (1×10⁻⁵ mol/l) reduced it to zero. The addition of both epinephrine and ergotamine at the latter concentrations restored the affinity of the fractions for Na⁺ and K⁺ to what it had been in the absence of the transmitter or antagonist, previously reported. Norepinephrine (3×10⁻¹⁰ mol/l), or ouabain (1×10⁻⁷ mol/l) reduced the affinity of the fraction for Na⁺ and K⁺ to zero. Thus, the transmitters and antagonists altered the affinity of the insoluble fraction for Na⁺ and K⁺ nonlinearity, dependent upon their concentrations, the concentrations of the cations, and the interaction of transmitter and antagonist.