Nicardipine enantiomers inhibit calcium and outward currents in rat pars intermedia cells.
The whole-cell patch clamp technique was used to investigate the effect of the dihydropyridine antagonist nicardipine and its two enantiomers on calcium and outward currents in rat pars intermedia cells. Inward voltage-activated calcium currents as well as outward currents were blocked by nicardipines (enantiomers and racemic substance). We found a highly significant correlation between the blockage of voltage-activated currents and outward currents, indicating an association between recorded currents. Therefore, the inhibitory effect of nicardipines was measured as outward current inhibition. The effects of (-) and (+) enantiomers as well as the racemic nicardipine were concentration-dependent. The (+)-enantiomer was the least potent with an ED50 of 3.8 +/- 1.2 microM, while the (-)-enantiomer inhibited currents with an ED50 of 0.7 +/- 0.1 microM. Racemic nicardipine blocked currents with an ED50 of 2.2 +/- 0.6 microM.
Kocmur-Bobanović
L
L
Laboratory of Neuroendocrinology, Institute of Pathophysiology, School of Medicine, Ljubljana, Slovenia.
Zorec
R
R
D000818:Animals; D015220:Calcium Channels / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D008297:Male; D009529:Nicardipine / Q000494:pharmacology*; D018408:Patch-Clamp Techniques; D010902:Pituitary Gland / Q000187:drug effects*; D051381:Rats; D013997:Time Factors
D015220:Calcium Channels; D009529:Nicardipine