TURNOVER INVIVO OF ALPHA1-ADRENERGIC RECEPTORS IN RAT SUBMAXILLARY-GLANDS

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  • 1 January 1983
    • journal article
    • research article
    • Vol. 23  (2) , 282-288
Abstract
In submaxillary glands, vas deferens and cerebral cortex, [3H]prazosin labeled one homogeneous population of .alpha.1-adrenergic receptors having a Kd of 0.1 nM. Injections of phenoxybenzamine i.v. blocked these receptors in a dose-dependent manner without changing the affinity of the remaining sites for [3H]prazosin. The phenoxybenzamine efficiency was highest in submaxillary glands: 1 mg/kg completely blocked the .alpha.1-adrenergic receptors but did not affect .alpha.2-adrenergic, .beta.-adrenergic and muscarinic receptors in this organ. After this blockade, the .alpha.-adrenergic receptors reappeared in the glands following a monoexponential time course. Analysis of this time course allows the determination of the rate constant for receptor degradation (k = 0.02 h-1) and the rate of receptor production (r = 1.86 fmol/mg of protein per h). The half-life of the receptor was 33 h. The reappearing receptors corresponded to newly synthetized receptors since their reappearance was blocked by i.p. injections of cycloheximide. Blockade of .alpha.1-adrenergic receptors with phenoxybenzamine (2 mg/kg) did not affect receptor reappearance. Higher doses (4-20 mg/kg) decreased the velocity of receptor reappearance.