Extracellular acidification related to the stimulation of catecholamines release by strontium in the bovine adrenal medulla.

The possible modifications of extracellular pH associated with the secretion of catecholamines evoked by the introduction of 2.2 mM Sr2+ to a Ca(2+)-free, buffer-free, Locke solution were investigated in decorticated perfused bovine adrenal glands. A progressive and reversible decrease of external pH accompanied the catecholamine release promoted by Sr(2+)-introduction into the perfusion fluid.

Effect of hyperosmolarity on extracellular acidification associated with catecholamine secretion evoked by barium in perfused bovine adrenal medulla.

1. The effects of the increase of osmotic strength on extracellular pH modifications produced during buffer-free, 5 mM Ba2+ stimulation was studied in decorticated perfused bovine adrenal glands. 2.

Characterization of extracellular pH drop due to the activation of the secretory process by acetylcholine in the bovine adrenal medulla.

A progressive and reversible decrease of external pH accompanied the catecholamine release elicited by acetylcholine in decorticated bovine adrenal glands perfused with buffer-free Locke solution adjusted to an initial pH of 7.4. Both the secretory response as well as the extracellular acid shift promoted by the cholinergic agonist were antagonized by hexamethonium plus atropine, Mg2+ and verapamil.

In vitro evaluation of acute effects of mitoxantrone (Novantrone) in rat and guinea pig atria.

Since guinea pig and rat atria have been used as models to study acute anthracycline-induced cardiotoxicity, experiments were carried out in these preparations to evaluate possible acute cardiac effects mediated by mitoxantrone (MTX). After a latency period of approximately 90 min, MTX (10(-5)-10(-4) M) promoted a concentration-related and time-dependent decrease of spontaneous rate in guinea pig atria. A similar but less intense effect after a longer latency interval was observed in rat atria.

Decrease of extracellular pH associated with the secretion of catecholamines induced by barium in perfused bovine adrenal medulla.

1. The possible modifications of extracellular pH produced during buffer-free 5 mM Ba2+ stimulation was studied in decorticated perfused bovine adrenal glands. 2.

Enhanced angiotensin converting enzyme binding in arteries from spontaneously hypertensive rats.

Aim: To localize and measure angiotensin converting enzyme (ACE) in different vascular beds of genetically hypertensive rats.

Methods: Quantitative autoradiography using the angiotensin converting enzyme (E.C.

Comparison of acute effects of mitoxantrone and doxorubicin in guinea-pig atria.

1. The acute effects of doxorubicin (DOX) and mitoxantrone (MTX) on basal rate and on positive chronotropic activity induced by 1-noradrenaline (1-NA) were investigated in isolated guinea-pig atria. 2.

Estrogens regulate angiotensin-converting enzyme and angiotensin receptors in female rat anterior pituitary.

We studied the effects of the estrous cycle, ovariectomy and estrogen replacement on angiotensin-converting enzyme (ACE) (kininase II, EC 3.4.15.

Autoradiographic localization and quantification of rat heart angiotensin converting enzyme.

Quantitative autoradiography with the angiotensin converting enzyme inhibitor [125I]351A revealed the presence of specific binding for this enzyme in the valve leaflets of the rat heart and in the aortic wall. Branches of the coronary arteries showed binding localized throughout the arterial walls. Binding was also present in the heart atria, where it was four-fold higher than in the heart ventricles.

Increased beta 2-adrenoceptors in the superior cervical ganglia of genetically hypertensive rats.

[125I]Iodocyanopindolol binding sites were characterized by autoradiography in the superior cervical ganglia of Wistar-Kyoto (WKY) rats. A high concentration of (-)-[125I]iodocyanopindolol binding sites, characterized as beta-adrenoceptors by (-)-propranolol displacement, was distributed throughout the ganglia and in the postganglionic (internal carotid) nerve. ICI 118,551, a beta 2-selective antagonist, displaced more than 85% of the binding sites, whereas CGP 20712A, a beta 1-selective antagonist, displaced less than 10% of the binding sites, indicating that the beta-adrenoceptors were primarily of the beta 2-subtype.

Inhibitory effect of hyperosmolality on catecholamine secretion from the bovine adrenal medulla.

We examined the effect of hyperosmolality on exocytotic catecholamine secretion in isolated-perfused bovine adrenals, in both the absence and presence of Ca2+ in the extracellular medium. Exposure of adrenal glands to hyperosmotic media (600 mOsm/Kg H2O) for 20 minutes significantly decreased spontaneous catecholamine output, and was independent of extracellular Ca2+ concentration. Adrenal glands were exposed to a hyperosmotic Locke solution (600 mOsm/Kg H2O) for 10 minutes and then stimulated with acetylcholine.

Different inhibitory sites of action for magnesium and verapamil in the bovine adrenal medulla.

The effects of verapamil and Mg2+ on catecholamine release induced by the substitution of NaCl by sucrose in the extracellular medium were studied in the perfused bovine adrenal medulla. Verapamil (3 X 10(-4) M) totally blocked the acetylcholine-evoked release of amines, but failed to antagonize the secretory response promoted by NaCl-omission. Perfusing glands with a Locke solution containing 10 mM Mg2+, produced a 61.