Laminar shear stress (LS) increases KCa3.1 and KCa2.3 expression in endothelial cells (ECs). Human coronary artery ECs (HCAECs) were exposed to static culture (ST), oscillatory shear stress (OS), or LS condition for 24 h, and the mRNA expression levels of each KCa subtype were compared based on the number of copies per 104 GAPDH mRNA. Under ST condition, transcripts for KCa2.2 and KCa2.3 were predominantly expressed compared with the other subtypes, whereas OS-exposed cells showed a moderate expression of KCa2.3. In contrast, KCa2.3 and KCa3.1 were the primary KCa subtypes after exposure to LS. aSignificant difference vs. KCa1.1, KCa2.1, and KCa3.1 in ST (P < 0.05). bSignificant difference vs. KCa1.1, KCa2.1, KCa2.2, and KCa3.1 in OS (P < 0.05). cSignficant difference vs. KCa1.1, KCa2.1, and KCa2.2 in LS (P < 0.05). *Signficant difference vs. ST (P < 0.05). #Signficant difference vs. OS (P < 0.05).