Do calcimimetics normalize the phosphate-induced stimulation of PTH secretion in vivo and in vitro?
Calcimimetics overcome the stimulatory effect of high phosphate on PTH secretion in vivo and in vitro. Thus, calcimimetics should be effective in patients with secondary hyperparathyroidism whose phosphorus levels would contraindicate vitamin D treatment alone.
The impairment in contractile responses to dobutamine and norepinephrine in DCM is associated with impaired myocardial O(2) extraction, and a shift toward a preference for glycolysis. A different myocardial metabolic pattern suggestive of increased oxidation of FFA with increased myocardial O(2) extraction was observed in the presence of combined beta(1)/beta(2) stimulation with isoproterenol or beta(2) stimulation (ISO+MET). These data suggest that beta(2)-AR stimulation in DCM shifts substrate preference toward FFA oxidation associated with greater M(v)O(2) requirements. These findings identify a putative metabolic effect of beta(2) -AR in DCM that may be deleterious.