[Sarcoplasmic reticular calcium release and myocardial protection--effects of ryanodine and cold cristalloid cardioplegia on hypothermic global ischemia].

Myocardial rapid cooling is known to result in sarcoplasmic reticular (SR) calcium release. SR calcium release during an infusion of cold cardioplegic solution may contribute to myocardial protection against hypothermic global ischemia. We have, therefore, investigated using the isolated working rat heart preparation to determine the effect of cold cristalloid cardioplegic solution (K+ = 16 mmol/L) containing ryanodine on myocardial injury due to hypothermic global ischemia. Hearts (n = 6-12/group) from male Wistar rats were aerobically (37 degrees C) perfused (20 min) with bicarbonate buffer (Ca2+ = 2.4 mmol/L). This was followed by a 3 min infusion of St. Thomas' Hospital cardioplegic solution (20 degrees C) containing various concentrations of ryanodine. Hearts were then subjected to 180 min of hypothermic (20 degrees C) global ischemia and 35 min of normothermic (37 degrees C) reperfusion (15 min Langendorff, 20 min working). The recoveries of aortic flow were 46.4 +/- 3.7% in the ryanodine free controls versus 50.8 +/- 5.1, 50.6 +/- 4.8, 53.1 +/- 5.9, 59.4 +/- 1.9, 50.5 +/- 3.2 and 31.8 +/- 6.1% in the 0.18, 0.88, 1.31, 1.75, 10.00 and 100.00 nmol/L ryanodine groups, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)