The effects of cyanide and iodoacetate intoxication and ischaemia on enzyme release from the perfused rat heart

There is a sudden release of intracellular constituents upon reoxygenation of isolated perfused hypoxic heart tissue (O2 paradox) or on perfusion with calcium-free medium after a period of hypoxia. Rat hearts were perfused by the method of Langendorff (Pfluegers Arch. 61: 291-332, 1895) with Krebs-Henseleit medium containing 10 mM glucose. Hearts were equilibrated for 30 min, followed by 90 min of hypoxia or 60 min of hypoxia and 30 min of reoxygenation. The massive enzyme release observed upon reoxygenation after 60 min of hypoxia was prevented by infusing 0.5 or 5 mM cyanide 5 min before reoxygenation. Lactate dehydrogenase (LDH) release commenced immediately upon withdrawal of cyanide. Hearts perfused with calcium-free medium throughout hypoxia did not release increased amounts of LDH at reoxygenation. Perfusing heart tissue with medium containing 0 or 25 microM calcium, but not 0.25 or 2.5 mM, after 50 min of hypoxia initiated a release of cardiac LDH, which was not further enhanced by reoxygenation. Enzyme release was significantly inhibited when the calcium-free perfusion medium included 10 mM 2-deoxyglucose (replacing glucose), 0.5 mM dinitrophenol, or 2.5 mM cyanide. Histologically, hearts perfused with calcium-free medium after 50 min of hypoxia showed areas of severe necrosis and contracture without any evidence of the contraction bands that were seen in hearts reoxygenated in the presence of calcium. Cardiac ATP and creatine phosphate (PCr) levels were significantly decreased after 50-60 min of hypoxia.(ABSTRACT TRUNCATED AT 250 WORDS)

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The Effect of β-Adrenergic Agonists on Enzyme Release from the Hypoxic Isolated Perfused Rat Heart

Biochemical Society Transactions ◽

10.1042/bst0030422 ◽

1975 ◽

Vol 3 (3) ◽

pp. 422-425 ◽

Cited By ~ 6

Author(s):

DAVID J. HEARSE ◽

PAMELA B. GARLICK ◽

JOHN P. SHILLINGFORD

Keyword(s):

Rat Heart ◽

Enzyme Release ◽

Adrenergic Agonists ◽

Perfused Rat Heart ◽

Isolated Perfused Rat Heart

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Serum requirement for release of heparin-induced lipase from perfused rat heart

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1964.206.3.610 ◽

1964 ◽

Vol 206 (3) ◽

pp. 610-614 ◽

Cited By ~ 12

Author(s):

M. F. Crass ◽

H. C. Meng

Keyword(s):

Rat Heart ◽

Lipolytic Activity ◽

Coconut Oil ◽

Cottonseed Oil ◽

Lipolytic Enzyme ◽

Enzyme Release ◽

Perfusion Medium ◽

Bicarbonate Buffer ◽

Oil Emulsion ◽

Perfused Rat Heart

The release of a lipolytic enzyme from the isolated perfused rat heart was studied. The perfusion medium was a Krebs-Henseleit bicarbonate buffer, pH 7.4, with or without heparin and/or serum. The lipolytic activity of perfusates was determined by incubating the perfusate in a phosphate buffer, pH 7.4, at 37 C for 1 or 2 hr using coconut oil emulsion, rat chylomicrons, or cottonseed oil emulsion as a substrate in the presence of serum albumin. Both heparin and serum were required for optimal enzyme release; the optimal concentrations of heparin and serum were 50 µg/ml and 10% by volume, respectively. Addition of serum to the assay system could not replace its effect in the perfusion medium. The appearance of the enzyme in the perfusion medium was rapid; 55% of the total lipolytic activity was released within 2 min. The lipolytic activity of this enzyme was inhibited by protamine, NaCl, NaF, and taurocholate.

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