Acta Physiologica et Pharmacologica Latinoamericana

The effect of pH on [3H]-DHA specific binding and its displacement by various nonlabeled ligands from beta-adrenoreceptors was examined in sarcolemmal membranes from canine hearts. At low pH (6.69) the affinity of beta-adrenoreceptors for agonists is lower than at pH 7.65, causing a 1.50-fold increase in the inhibition constant (KI) of both (-) noradrenaline and (-) isoprenaline. The change in the affinity was attenuated by adding 300 microM GTP to the reaction medium. Low pH neither affected the affinity of antagonists ((-) dihydroalprenolol, (+/- ) alprenolol, ( +/- ) propranolol) for adrenoreceptors nor the number of binding sites determined by [3H]-DHA binding assays. The effect of pH suggests that H+ induces the formation of a low affinity state of beta-adrenoreceptors for agonists. This H+-dependent mechanism may be capable of regulating the process by which agonists stimulate adenyl cyclase.

Gende Oa

Camilión de Hurtado Mc

Cingolani He

Acta physiologica et pharmacologica latinoamericana

Effect of pH changes on the binding of agonists and antagonists to the adrenergic beta receptor

pH变化对激动剂和拮抗剂与肾上腺素β受体结合的影响

The aim of the present study has been to examine the effects of superior cervical ganglionectomy (SCGx) on the hypertrophic (thyroid lobe weight) and hyperplastic (thyroid mitotic activity) response of the rat thyroid gland in basal conditions or after hemithyroidectomy (hemiTx), both being assessed 14 days after the surgeries. It has been shown that: 1) Ipsilateral and/or bilateral SCGx brought about the growth (both hypertrophy and hyperplasia) of thyroid lobes in the animals with intact thyroid; the strongest hypertrophic reaction occurred after ipsilateral SCGx and the strongest hyperplastic response followed bilateral SCGx. 2) Unilateral SCGx, when performed ipsilaterally to the remaining thyroid lobe after hemiTx amplified the hypertrophic, but not hyperplastic response of this lobe. Both contralateral and bilateral SCGx had no effect on the hypertrophy of the remaining thyroid lobe. Unexpectedly, both bilateral and contralateral SCGx exerted the suppressive effect on the hyperplastic response of the thyroid lobe following hemiTx. These results indicate that the sympathetic innervation plays an important role in the control of thyroid growth of intact animals and/or after hemiTx.

G Zerek Melen

A Lewinski

Influence of sympathetic derivation of the thyroid by superior cervical ganglionectomy on the growth processes in the gland in basal conditions and after hemithyroidectomy

上颈神经节切除术对甲状腺交感神经支配的影响及其在基础条件和甲状腺半切除术后对腺体生长过程的影响

To obtain information on the sites and mechanisms of the myoneural effect of aminoglycoside and polypeptide type antibiotics, the influence of neomycin, streptomycin, gentamicin and polymyxin B on the depression of the force of contraction (P) of the rat phrenic nerve-hemidiaphragm preparation was investigated at 37 degrees C, 27 degrees C or 17 degrees C and also at 37 degrees C in electrolyte solutions containing 2.5, 1.25 or 0.625 mM CaCl2. Decreasing the temperature or the CaCl2 concentration ((CaCl2)o) of the bath significantly (p less than 0.001) decreased P. The depressant effect of aminoglycosides on P (about 50% of control at 17 degrees C) was increased more with lower temperatures than that of polymyxin B (about 20%). The effect of lowering the (CaCl2)o on the depression of P (about 90% of control at the lowest (CaCl2)o) was about the same with the 4 antibiotics. The development of the maximal effect and the recovery of P after washout was slower with polymyxin B than with the 3 aminoglycosides. 4-Aminopyridine antagonized the depression of P caused by polymyxin B less than that caused by aminoglycosides. The findings suggest that aminoglycosides depress myoneural activity primarily by inhibiting stimulated release of ACh. Polymyxin B also inhibits ACh release, but inhibition of the contraction of myofibrils contributes more significantly to its myoneural effects than with aminoglycosides. It is conceivable that blocking of the ionophores of the postjunctional membrane also contributes to the myoneural effects of polymyxin B.

Foldes Ff

Bikhazi Gb

The influence of temperature and calcium concentration on the myoneural effect of antibiotics.

温度和钙浓度对肌肉神经抗生素效应的影响。

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Effect of pH changes on the binding of agonists and antagonists to the adrenergic beta receptor

Influence of sympathetic derivation of the thyroid by superior cervical ganglionectomy on the growth processes in the gland in basal conditions and after hemithyroidectomy

The influence of temperature and calcium concentration on the myoneural effect of antibiotics.

The influence of temperature and calcium concentration on the myoneural effect of antibiotics.

Influence of sympathetic derivation of the thyroid by superior cervical ganglionectomy on the growth processes in the gland in basal conditions and after hemithyroidectomy

Effect of pH changes on the binding of agonists and antagonists to the adrenergic beta receptor