Capillary and cell wall permeability to potassium in isolated dog hearts.
From venous tracer-dilution curves recorded after 36 pulse injections of 42KCl and 131I-labeled albumin into the coronary artery inflow of 15 isolated canine heart preparations, we calculated maximal fractional extractions (Emax) and capillary permeability-surface area products (PScap) for 42K+ over a range of plasma flows (FP) from 0.3 to 1.7 ml min-1 g-u. At low FP (less than 1.0), Emax was 0.60 +/- 0.0l (mean +/- SD) and PScap was 0.72 +/- 0.20 ml min-1 g-1; at high FP (greater than 1.0), Emax decreased to 0.49 +/- 0.05 and PScap increased to 1.06 +/- 0.18. Continuous recording (gamma detector) of residual myocardial 42K+ in seven hearts showed that the mean fractional escape rate of tracer between 30 and 60 min after injection was 0.011-0.023 min-1; higher rates were observed at high FP, when the residue of 42K+ decreased to less than 10% of the injected dose by 60 min. Using PScap measured at high FP and considering the virtual intracellular volume of distribution for K+ to be 20 ml/g, we calculated the permeability-surface area product for sarcolemma (PScw) as 0.54-0.73 ml min-1 g-1, or about 50% of PScap. Considering sarcolemmal surface area (Scw) as 4,200 cm2/g and capillary surface area (Scap) as 500 cm2/g, cell permeability is low, with Pcw:Pcap being less than 0.08.
D000818:Animals; D001783:Blood Flow Velocity; D001786:Blood Glucose / Q000032:analysis; D002199:Capillary Permeability; D002200:Capillary Resistance; D002463:Cell Membrane Permeability; D003331:Coronary Vessels / Q000378:metabolism; D004285:Dogs; D006321:Heart / Q000033:anatomy & histology; D006400:Hematocrit; D066298:In Vitro Techniques; D009206:Myocardium / Q000378:metabolism*; D009929:Organ Size; D010477:Perfusion; D011188:Potassium / Q000008:administration & dosage / Q000097:blood / Q000378:metabolism*
D001786:Blood Glucose; D011188:Potassium