Background:

(S)-(-)-Bay-K-8644 is an agonist of L-type Ca2+ channel. (S)-(-)-Bay-K-8644 activates Ba2+ currents (IBa) (EC50=32 nM).

(±)-Bay K 8644, a conventional racemic mixture of Bay K 8644, is widely used as an L-type Ca2+ channel agonist. Each optical isomer possesses opposite effects on IBa (R(+)-Bay K 8644 as an antagonist and (S)-(-)-Bay-K-8644 as an agonist. (S)-(-)-Bay-K-8644 can prevent the inhibitory actions of two distinct cyclic nucleotide pathways on IBa in gastric myocytes of the guinea pig antrum[1]. The Ca2+ channel activity is enhanced by 3–30 μM (S)-(-)-Bay-K-8644 an agonist of L-type Ca2+ channels[2]. The interactions of two Ca2+ channel activators (S)-(-)-Bay-K-8644 and FPL 64176 is examined on smooth muscle L-type Ca2+ channels. FPL 64176 (300 nM) causes a sustained contraction of rat tail artery strips. This contractile response is inhibited by approximately 70% by (S)-(-)-Bay-K-8644 (EC50=14 nM). (S)-(-)-Bay-K-8644 (100 nM) increases whole-cell Ca2+ currents in A7r5 smooth muscle cells but effectively blocks further stimulation by 1 μM FPL 64176[3].

参考文献:
[1]. Zhu HL, et al. Antagonistic actions of S(-)-Bay K 8644 on cyclic nucleotide-induced inhibition of voltage-dependent Ba(2+) currents in guinea pig gastric antrum. Naunyn Schmiedebergs Arch Pharmacol. 2008 Dec;378(6):609-15.
[2]. Mironov SL, et al. L-type Ca2+ channels in inspiratory neurones of mice and their modulation by hypoxia. J Physiol. 1998 Oct 1;512 ( Pt 1):75-87.
[3]. Rampe D, et al. Functional interactions between two Ca2+ channel activators, (S)-Bay K 8644 and FPL 64176, in smooth muscle. Mol Pharmacol. 1992 Apr;41(4):599-602.