| RESEARCH PAPER
|Year : 1998 | Volume
| Issue : 2 | Page : 82-88
Interaction of calcium channel blockers (CCBs) with noradrenaline and terbutaline on isolated right ventricle from normal and diseased rats
Bhugra Praveen, OD Gulati
Objective: To investigate the interaction of calcium channel blockers (CCBs) with noradrenaline (NA) and terbutaline (TA) in rat isolated right ventricle preparations.
Methods: Ventricles were obtained from control rats, DOCA-saline hypertensive rats and hyperthyroid rats treated chronically with diltiazem, nifedipine or nimodipine. Responses of isolated ventricles to NA and TA were recorded on polyrite using force displacement transducer.
Results: In control rats chronic treatment with diltiazem, nifedipine or nimodipine produced an increase in the pD2 value of NA and TA. In hypertensive rats there was an increase in the pD2 value of NA and TA with no change (NA) and increase (TA) in maxima. In chronic nifedipine or nimodipine treated hypertensive preparations the maximal responses to NA and TA were decreased with reduction of pD2 value of NA and no effect on that of TA. Microscopical observations of nifedipine treated hypertensive preparations produced restoration of the tissue damage to normal. There was increase in the pD2 value of both agonists in hyperthyroid preparations. Simultaneous treatment with L-thyroxine and CCBs produced decrease in pD2 values and maximal response to NA and no response to TA. Microscopical observation of hyperthyroid preparations treated with nimodipine produced normalization of the structure.
Conclusion: In control preparations treated with CCBs down-regulation of beta, receptor may be associated with upregulation of beta, receptors. The beneficial effects of CCBs in hypertension and hyperthyroidism may be due to down-regulation of beta-adrenoceptors.
Source of Support: None, Conflict of Interest: None