The effect of calcium and high-energy phosphate compounds on myocardial contracture in the newborn and adult rabbit

The effect of hypoxia on myocardial high-energy phosphate content in the newborn, 2-wk-old, and adult rabbit was determined and compared with mechanical function. Studies were done on the ventricular septum arterially perfused with Krebs-Henseleit bicarbonate buffer solution equilibrated with 95% O2 and 5% CO2 (control) or 95% N2 and 5% CO2 (hypoxia) at 60 beats/min and 27 degrees C. In the adult, ATP concentration decreased to 68%, 56%, and 39% of control after 2, 30, and 60 min of hypoxia, respectively. After 30 min of hypoxia, ATP concentration was not different from control in the newborn but decreased to 82% of control in the 2-wk-old. After 2 min of hypoxia, creatine phosphate concentration decreased to 55% and 10% of control in the newborn and adult rabbit, respectively. Lactate production increased significantly during hypoxia and was greater in the newborn than in the adult. The data indicate that the newborn rabbit is capable of maintaining glycolysis and normal levels of myocardial ATP during hypoxia, which ensures normal myocardial mechanical function for longer periods than in the adult.

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Utilization of High-Energy Phosphate Compounds by Stomach

The Journal of General Physiology ◽

10.1085/jgp.51.5.233 ◽

1968 ◽

Vol 51 (5) ◽

pp. 233-239 ◽

Cited By ~ 15

Author(s):

R. P. Durbin

Keyword(s):

High Energy ◽

High Energy Phosphate ◽

Phosphate Compounds

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Low sodium attenuation of the Ca2+ paradox in the newborn rabbit myocardium

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1985.248.3.h345 ◽

1985 ◽

Vol 248 (3) ◽

pp. H345-H349

Author(s):

S. Uemura ◽

H. Young ◽

S. Matsuoka ◽

J. M. Jarmakani

Keyword(s):

Rabbit Heart ◽

High Energy ◽

Adult Rabbit ◽

High Energy Phosphates ◽

Mechanical Function ◽

High Energy Phosphate ◽

Newborn Rabbit ◽

Low Sodium ◽

Resting Tension ◽

Rabbit Myocardium

The effect of low sodium (Na 24 mM) perfusate during Ca2+ depletion on mechanical function, tissue high-energy phosphate, creatine kinase (CK) release, and tissue potassium was studied in the arterially perfused newborn and adult rabbit heart. During Ca2+ depletion, the time for DT and +dT/dtmax to decline to half-maximal value in newborn muscles perfused with low Na (46 +/- 3 S) was significantly (P less than 0.05) longer than the value obtained with normal Na (14 +/- 1 S). Similar values were obtained in the adult. During Ca2+ repletion, the increase in resting tension and CK release was attenuated in the low Na groups, and the values in the newborn were significantly less than in the adult. The recovery of +dT/dtmax and tissue high-energy phosphates in the low Na groups were significantly greater than in the normal Na groups, and the values in the newborn were significantly greater than in the adult. These data suggest that low Na during the Ca2+-free period delays both cellular Ca2+ depletion during the Ca2+-free period and Ca2+ influx during Ca2+ repletion. This effect in the newborn is greater than in the adult and might be explained by Na+-Ca2+ exchange.

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