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T E Tenner

Publications and source records attributed to T E Tenner.

59 records · Page 4Linked to original sources
PubMed1978

Reserpine-induced supersensitivity to the chronotropic and inotropic effects of calcium in rabbit atria.

Supersensitivity to the chronotropic and inotropic effects of calcium was demonstrated in spontaneously beating paired atria from reserpine-pretreated (0.1 mg/kg/day, 7 days) rabbits. Supersensitivity to the inotropic effects of calcium in electrically driven left atria was also demonstrated. Atria were driven at 80, 100 and 120 beats/min. At each frequency the reserpine-pretreated atria were more sensitive than controls. Atria were tested under diastolic tensions of 1,2 and 4 g. As the tension was increased the sensitivity to calcium increased. The sensitivity of reserpine-pretreated atria was greater at each tension than that of control atria. Atria tested at 37 degrees C were less sensitive than those tested at 30 degrees C; however, the reserpine-pretreated atria were more sensitive than control atria at both temperatures. This study demonstrates that reserpine-induced supersensitivity to the inotropic effects of calcium can be obtained and that the ability to demonstrate this phenomenon does not appear to be altered by the frequency, diastolic tension or temperature at which each experiment is performed.

Animals↗
PubMed1976

Influence of magnesium on calcium- and potassium-related responses in vascular smooth muscle.

The influence of Mg on Ca- and K-related responses of rabbit aortic strips was studied. Aortic strips bathed in either a K-free or 60.0 mM K solution were less sensitive to Ca in the presence of 1.2 mm Mg. Ca induced greater maximum tension in the aortic strips in the presence of Mg when bathed in 60.0 mM K. Addition of K to a K-free medium induced a slight relaxation at low concentrations (is less than 1.0 mm) which was Ca dependent. The relaxation was less in the presence of Mg. Wiolution were less sensitive to Ca in the presence of 1.2 mm Mg. Ca induced greater maximum tension in the aortic strips in the presence of Mg when bathed in 60.0 mm K. Addition of K to a K-free medium induced a slight relaxation at low concentrations (is less thth Mg in the medium throughout the experiment (90 min), the threshold concentration of K, including a contractile response, was increased as was the maximum tension. Acute addition of Mg decreased the maximum response to K. When K was lowered from 5.4 to 0.0 mm a contractile response, absent in the presence of Mg, occurred. When the K was increased, the tension returned to baseline. At 25-30 mm K, the tension again increased, reaching a maximum at 40-50 mm K. Ca uptake was stimulated at all K concentrations producing a contraction. Mg depressed this increase in uptake. 45Ca efflux was more rapid into a 50.0 mm than into 0.0 mm K solution. Mg delayed Ca efflux. It is concluded from these data that Mg has two components in its effect on the Ca associated with K responses. One is a competition with Ca at extracellular sites probably at the membrane, and the other is intracellular, probably a competition with Ca at sequestration sites.

Animals↗