THE MECHANISM OF PACEMAKER ACCELERATION DUE TO INCREASED INTRA-ATRIAL PRESSURE IN THE ISOLATED ATRIUM

1962 ◽  
Vol 40 (1) ◽  
pp. 805-814 ◽  
Author(s):  
G. W. Mainwood
Keyword(s):  
Constant Pressure ◽  
Pressure Response ◽  
Ph Gradient ◽  
Atrial Pressure ◽  
Closed Circuit ◽  
Atrial Wall ◽  
Bicarbonate Concentration ◽  
Rat Atria ◽  
Increased Pressure ◽  
Isolated Rat

A closed circuit with a miniature pump was used to perfuse isolated rat atria through the lumen. The rate of spontaneous atrial potentials was measured continuously on a recording potentiometer.The response of the atrium to changes in luminal pressure was observed under a number of different conditions. The acceleration due to increased pressure was greatest when the perfusing fluid contained low bicarbonate concentrations (5–10 mmolar) and was very much reduced or abolished with 28 mmolar bicarbonate. Pacemaker rate at constant pressure varies directly with pH in the presence of high bicarbonate concentrations. The pressure response may be interpreted in terms of a pH gradient across the atrial wall which is dependent on the bicarbonate concentration and may be reduced by stretching the atrium.

THE MECHANISM OF PACEMAKER ACCELERATION DUE TO INCREASED INTRA-ATRIAL PRESSURE IN THE ISOLATED ATRIUM

1962 ◽  
Vol 40 (6) ◽  
pp. 805-814 ◽  
Author(s):  
G. W. Mainwood
Keyword(s):  
Constant Pressure ◽  
Pressure Response ◽  
Ph Gradient ◽  
Atrial Pressure ◽  
Closed Circuit ◽  
Atrial Wall ◽  
Bicarbonate Concentration ◽  
Rat Atria ◽  
Increased Pressure ◽  
Isolated Rat

A closed circuit with a miniature pump was used to perfuse isolated rat atria through the lumen. The rate of spontaneous atrial potentials was measured continuously on a recording potentiometer.The response of the atrium to changes in luminal pressure was observed under a number of different conditions. The acceleration due to increased pressure was greatest when the perfusing fluid contained low bicarbonate concentrations (5–10 mmolar) and was very much reduced or abolished with 28 mmolar bicarbonate. Pacemaker rate at constant pressure varies directly with pH in the presence of high bicarbonate concentrations. The pressure response may be interpreted in terms of a pH gradient across the atrial wall which is dependent on the bicarbonate concentration and may be reduced by stretching the atrium.

Release of ANF, proANF 1-98, and proANF 31-67 from isolated rat atria by atrial distension

1991 ◽  
Vol 260 (6) ◽  
pp. H1774-H1778 ◽  
Author(s):  
J. R. Dietz ◽  
S. J. Nazian ◽  
D. L. Vesely
Keyword(s):  
Baseline Level ◽  
Experimental Period ◽  
Atrial Pressure ◽  
Rat Atria ◽  
A Value ◽  
Isolated Atria ◽  
Krebs Buffer ◽  
Isolated Rat

The purpose of the present study was to determine if ANF and the NH2-terminus of the ANF prohormone are secreted simultaneously in response to atrial distension in isolated perfused rat atria. The experiments were conducted in paced left atria perfused with a modified Krebs buffer. Atrial pressure was increased from a baseline level of 2 mmHg to 8-9 mmHg for 60 minutes (distension) and then returned to 2 mmHg for 60 minutes in one group (n = 9) of isolated atria. In a second group of atria (n = 6), atrial pressure was maintained at approximately 2 mmHg throughout the experimental period. ANF secretion averaged 100 pg/min during the three 10-minute periods immediately preceding the increased atrial pressure and increased to 600-800 pg/min (P less than 0.001) when atrial pressure was raised. Secretion of the proANF 31-67 peptide increased from a value of approximately 100 pg/min immediately prior to distension to a peak of over 200 pg/min during distension (P less than 0.01). Secretion of proANF 1-98 increased from an average of 1.25 ng/min during the three periods immediately prior to distension to a peak of 2.5 ng/min during distension (P less than 0.01). These data indicate that ANF and the NH2-terminus of the ANF prohormone appear to be simultaneously secreted by isolated paced atria.

scholarly journals Neurotransmitter Control of Sinoatrial Pacemaker Frequency in Isolated Rat Atria and in Intact Rabbits

1970 ◽  
Vol 27 (6) ◽  
pp. 867-873 ◽  
Author(s):  
ALBERT S. GRODNER ◽  
HANS-GUNTHER LAHRTZ ◽  
PETER E. POOL ◽  
EUGENE BRAUNWALD
Keyword(s):  
Rat Atria ◽  
Isolated Rat

scholarly journals Influence of hypothyroid status on dopamine-induced positive chronotropic and inotropic effects on isolated rat atria.

1982 ◽  
Vol 32 (2) ◽  
pp. 221-230 ◽  
Author(s):  
Atsuko HIRANO ◽  
Hisakuni HASHIMOTO ◽  
Mitsuyoshi NAKASHIMA
Keyword(s):  
Inotropic Effects ◽  
Rat Atria ◽  
Isolated Rat

scholarly journals The relation between reduced protein degradation and elevated adenosine 3',5'-monophosphate in isolated rat atria.

1981 ◽  
Vol 49 (3) ◽  
pp. 609-617 ◽  
Author(s):  
D S O'Hara ◽  
G D Curfman ◽  
C G Trumbull ◽  
S M Sandler ◽  
T W Smith
Keyword(s):  
Protein Degradation ◽  
Rat Atria ◽  
Isolated Rat

Circadian Rhythms: Variation in Sensitivity of Isolated Rat Atria to Acetylcholine

Science ◽  
1966 ◽  
Vol 154 (3750) ◽  
pp. 782-782
Author(s):  
R. P. Spoor ◽  
D. B. Jackson
Keyword(s):  
Circadian Rhythms ◽  
Rat Atria ◽  
Isolated Rat

Atrial dynamics, atrial natriuretic factor, tachycardia, and blood volume in anesthetized rabbits

1991 ◽  
Vol 261 (1) ◽  
pp. H22-H28 ◽  
Author(s):  
K. A. King ◽  
J. R. Ledsome
Keyword(s):  
Blood Volume ◽  
Atrial Natriuretic Factor ◽  
Left Atrial ◽  
Wall Stress ◽  
Atrial Pressure ◽  
Right Atrial ◽  
Right Atrial Pressure ◽  
Atrial Wall ◽  
Natriuretic Factor ◽  
Atrial Natriuretic

The effects of tachycardia and a slow (1%/min) 20% reduction and elevation of blood volume (BV) on right atrial pressure (RAP), right atrial dimension (RAD), and plasma immunoreactive atrial natriuretic factor (IR-ANF) were examined in anesthetized rabbits. Plasma IR-ANF was significantly increased during pacing at 6 Hz in the presence of high BV but not at low BV. Mean RAP increased with expansion of BV, but this change was not associated with significant changes in IR-ANF. There were no statistically significant changes in systolic or diastolic RAD with alterations in BV or with tachycardia. Tachycardia had no effect on left atrial dimension. Diastolic right atrial wall stress (DRAS) and minute DRAS increased with a 20% increase in BV, but changes in BV did not affect systolic right atrial wall stress (SRAS) or minute SRAS. Tachycardia decreased DRAS at high BV and significantly increased SRAS and minute SRAS. The increases in SRAS and minute SRAS were greater during tachycardia at high BV, suggesting that an interaction between BV and tachycardia results in potentiation of SRAS and minute SRAS. The results suggest that systolic RAS is a significant factor in ANF release during tachycardia at high BV.

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