[The effects of phorbol 12-myristate 13-acetate and microcystine-LR on calcium channel in resistance vascular smooth muscle cells in SHRsp].

OBJECTIVE

To investigate the effects of phorbol 12-myristate 13-acetate (PMA) and microcystine-LR (MCYST-LR) on the whole-cell barium currenta of voltage-dependent calcium channels (VDCs) of the resistance vascular smooth muscle cells (VSMC) from the A4-A5 branches of mesenteric artery in stroke-prone spontaneously hypertensive rats (SHRsp) and its normotensive control Wistar rats.

METHODS

Using the whole-cell Ba2+ current recording of the patch clamp technique.

RESULTS

It was found that PMA, a protein kinase C (PKC) agonist or MCYST-LR, a protein phosphatase IA and IIA inhibitor by which the enhancement of phosphorylation induced could apparently activate the VDCs of the visceral resistance VSMC.

CONCLUSIONS

This activation would be significantly potentiated during hypertension, in which the increase of L-type calcium channel openings induced by PMA was obviously manifest, as the T-type calcium channel activity weakly potentiated. In normotensive Wistar rats, the increase of T-type calcium channel openings was greater than that of SHRsp. However, the effect of MCYST-LR appeared that only the increase of L-type calcium channel current in SHRsp was significant. It is suggested that the action of PKC and/or phosphorylation on the different components of calcium currents should be emphasized in the investigation of the mechanism in the increase in peripheral resistance during hypertension.