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Biomedical subjects

M Decrinis

Publications and source records attributed to M Decrinis.

39 records · Page 3Linked to original sources
PubMed1989

Effects of endothelin on the cardiovascular system and on smooth muscle preparations in different species.

(1) The actions of porcine endothelin (ET), an endothelium-derived vasoconstrictor peptide, have been investigated in several in vitro smooth and cardiac muscle preparation as well as on the blood pressure of anaesthetized rats and rabbits. (2) In isolated visceral smooth muscles (guinea pig ileum, rat colon and uterus, rabbit jejunum) ET caused a long-lasting contraction which persisted after repeated rinsing. ET did not interfere with the spontaneous phasic activity of the rabbit jejunum or with contractions evoked by histamine or carbachol. (3) ET contracted isolated blood vessels (portal vein of guinea-pig and rat). In isolated perfused organs (rabbit ear, guinea-pig lung, rat mesentery and hindpaw) ET led to a long-lasting vasoconstriction. In the isolated perfused guinea-pig lung ET caused vaso- and bronchoconstriction. (4) ET produced a long-lasting positive inotropic effect in spontaneously beating isolated guinea-pig atria. The positive inotropic action of strophanthin was augmented in the presence of ET. (5) In the isolated perfused guinea-pig and rat hearts the prominent effect of ET was a long-lasting coronary vasoconstriction. (6) Pithed rats responded to i.v. injection of ET with a long-lasting increase in blood pressure. In pentobarbitone anaesthetized rats pretreated either with atropine, with guanethidine plus atropine, or with guanethidine plus atropine plus indomethacin, the long-lasting increase in blood pressure was smaller than in pithed rats whereas the initial short-lasting decrease in blood pressure was more pronounced; in pentobarbitone anaesthetized rabbits endothelin caused bronchoconstriction, a decrease in blood pressure and a pronounced increase in central venous pressure possibly resulting from pulmonary or coronary artery constriction or a combination of both effects.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMedDate not supplied

Effects of adenosine on electrical activity of isolated guinea pig hearts.

Negative chronotropic and dromotropic effects of adenosine seem to be responsible for its antiarrhythmic action on supraventricular tachyarrhythmias. To further characterize the effects of adenosine on supraventricular arrhythmias heart rate, conduction, refractoriness, the time to steady-state of AV-nodal conduction slowing and of sinus rate reduction were evaluated. Changes of heart rate, conduction intervals and effective refractory periods were determined by the use of a high-resolution ECG recording technique in isolated guinea pig hearts perfused by the method of Langendorff. Adenosine in concentrations of 3 and 10 microM reduced sinus rate and prolonged AV-nodal conduction significantly, while intraventricular and His bundle conduction were not altered. The maximal effect of adenosine on the sinus node and AV nodal conduction occurred after 636 +/- 109 and 111 +/- 35 (mean +/- SE) beats, respectively. During programmed stimulation at a cycle length of 250 ms, adenosine reduced atrial ERP in a dose-dependent manner. At cycle lengths of 170 and 200 ms, adenosine increased the atrial ERP at 3 microM, and then progressively shortened the ERP at higher doses. At all adenosine concentrations used, the usual rate-dependent adaption in ERP was suppressed. These observations explain the efficacy of adenosine against supraventricular tachyarrhythmias where the AV-node forms a part of a reentrant circuit. Adenosine shortened the atrial ERP, but at high pacing rates also led to a relative prolongation of the atrial ERP as the rate-dependent adaption was suppressed. These opposite effects of adenosine may explain earlier contradictory findings of its action on atrial arrhythmias.

Adenosine↗