Reports differ as to the efficacy of
glucose and
insulin as cardioplegic additives. Although deliberate oxygenation of
crystalloid cardioplegic solutions improves myocardial protection, little is known about the protection afforded by
glucose and
insulin in such oxygenated solutions. In the isolated working rat heart, we studied the addition of
oxygen,
glucose, and
insulin, separately and together, to a
cardioplegic solution. The
solution was equilibrated with O2 or N2, with
glucose added as a substrate or
sucrose as a nonmetabolizable osmotic control, with or without
insulin. Hearts were arrested for 2 hours at 8 degrees C by multidose infusions. Oxygenation decreased
lactate production and improved high-energy
phosphate and
glycogen preservation during arrest, prevented
ischemic contracture, and improved functional recovery. The addition of
glucose to the oxygenated
solution increased the level of
adenosine triphosphate at end-arrest from 10.5 +/- 0.5 to 13.9 +/- 0.6 nmol/mg dry weight and
glycogen stores from 18.7 +/- 2.5 to 35.7 +/- 5.5 nmol/mg dry weight. The further addition of
insulin did not better preserve these metabolites. Improvements in functional recovery due to
glucose or
insulin in the oxygenated
solution attained statistical significance when both additives were included.
Glucose increased
lactate production significantly only when the
solution was nitrogenated.
Insulin added to the nitrogenated
glucose-containing
solution increased
adenosine triphosphate and
glycogen levels after 1 hour of arrest; and, although
insulin did not prevent
ischemic contracture from developing during the latter part of arrest with profound depletion of these metabolites, functional recovery was improved. The mechanism of improved functional recovery by
insulin is not clear.(ABSTRACT TRUNCATED AT 250 WORDS)