Bay K 8644

Bay K 8644 ((±)-Bay K 8644) is a racemate consisting of two isomers (R)-(+)-Bay-K-8644 and (S)-(-)-Bay-K-8644^[1]. Bay K 8644 is a L-type Ca²⁺ channel agonist with an EC₅₀ of 17.3 nM. Bay K 8644 increases Ca²⁺ influx through sarcolemmal Ca²⁺ channels by increasing the open time of the channel. Bay K 8644 has vasoconstrictive effects^[2][3]. In Vitro: In newborn rat ventricular cardiomyocytes, Bay K 8644 (1 μM) treatment increases L-type calcium current density in 2-day-old cells. The higher increase of L-type calcium current density by Bay K 8644 in 2-day- than in 7-day-old cultured cells could be interpreted as the result of a difference in the phosphorylation level of calcium channels for each stage of development^[4]. In Vivo: A one time dose as low as 10 μg/kg of Bay K 8644 significantly elevates mean arterial pressure (MAP) in endotoxin-treated hypotensive rats while having minimal effects in normal rats. Bay K 8644 also causes a dose-dependent decrease in heart rate of 37% in endotoxin-treated rats and 39% in control rats^[5].