Intra- and extracellular markers in interstitial transudate of perfused rat hearts.

The interstitial transudate was investigated in isolated perfused rat hearts. Capillary permeability and the kinetics of interstitial uptake and release were characterized using four different marker molecules (mol wt 522 to 2 X 10(6)). The half-time (t1/2) values (less than 30 to 170 s) and the interstitial concentration after 30 min (100-44% of arterial concentration) reflected the order and inverse order of their molecular weights, respectively. Creatine kinase (CK) and glutathione (GSH) were measured during control state, hypoxia, and anoxia, followed by reoxygenation. Interstitial concentrations of CK and GSH were higher by a factor of 100 and 8, respectively, compared with the venous effluent. During hypoxia (PO2 = 110 mmHg, i.e., O2 supply = 30% of demand) and reoxygenation there was a significant increase only in the interstitial (not venous) release of CK and GSH, which was further increased during anoxia. Ischemia (75 min) and reperfusion cause no interstitial release of lysosomal (acid phosphatase) and mitochondrial (glutamate dehydrogenase) enzymes despite a massive loss of cytosolic enzymes. Examination of the interstitial transudate allows characterization of capillary transfer and provides a very sensitive measure of sarcolemmal release phenomena.