?-adrenoceptor desensitization and changes of calcium transient in rat ventricular myocytes following chronic hypoxia / 中国病理生理杂志

ABSTRACT

AIM: The present study was to investigate the time course of ?-adrenoceptor desensitization and changes in the calcium transient in rat ventricular myocytes following chronic hypoxia. METHODS: With the spectrofluorometric method, the intracellular calcium( i) transient and its response to ?-adrenoceptor stimulation were determined in the single right ventricular myocytes, loaded with Fura-2.RESULTS: After 2-3 weeks of chronic hypoxia, the amplitudes of electrically induced i transient and caffeine-induced i transient started to decrease and the duration of i transient prolonged. The enhanced electrically induced i transient evoked by isoprotrenol was also decreased. After 3 or 4 weeks of chronic hypoxia, these changes aggravated gradually. After 8 weeks of chronic hypoxia, the changes of all these parameters were convalescent, meanwhile there was no significant difference compared with that of 4 weeks group. CONCLUSIONS: After 2-4 weeks of chronic hypoxia, the ?-adrenoceptor desensitization occurs, the underlying mechanism is related to the decreased function of L-type of calcium channel, ryanodine receptor-operated calcium channel and calcium ATPase, which is responsible for the decreased cardiac functionl. At 8 weeks of hypoxia, the heart is in adaptation and compensatory process.