Voltage-dependent potassium channels in cytokeratin-positive and cytokeratin-negative microvascular endothelial cells of the corpus luteum

Abstract.

We have recently described cytokeratin-positive (CK⁺) and cytokeratin-negative (CK^–) microvascular endothelial cells (MVECs) in the bovine corpus luteum. The two phenotypes show a different expression and release of adhesion molecules and cytokines. Since secretion of mediators is specifically regulated by the electrophysiological membrane parameters, this report will compare voltage-dependent potassium (K⁺) channels in the two cell types cultured under the same conditions. CK⁺ and CK^– MVECs derived from the microvascular bed of one organ differ in their K⁺-channel characteristics. In CK^– MVECs, an inwardly rectifying K⁺ current was discovered, showing the characteristics of the Kir2.1. CK⁺ MVECs displayed a voltage-dependent K⁺ current that activates rapidly on depolarization and inactivates very slowly, and is associated with a member of the Kv family. The mRNA for Kir2.1 was identified by RT-PCR in CK^– and CK⁺ MVECs, but there was no evidence of Kv1.4 mRNA in either of them. The function of Kir2.1 in CK^– MVECs might be induced during cultivation, whereas CK⁺ MVECs appear to be more resistant to environmental conditions and do not express an inward current.