抄録
To clarify the mechanism by which high concentration of cAMP decreases L-type Ca2+channel current (ICa(L)) in vascular smooth muscle (VSM) cells (A7r5), ICa(L) was recorded by whole-cell voltage clamp using a patch-clamp technique. 5 mM BaCl2 was used as a charge carrier to record ICa(L). Forskolin (FSK, 100 μM) decreased ICa(L) by 30%. When measured FSK-induced inhibition of ICa(L) after pretreatment with H-89 (PKA inhibitor) or KT5823 (PKG inhibitor), H-89 partially abolished the FSK inhibition by 30% and KT5823 further abolished by 77%. When the expression of type Iβ protein kinase G (PKG Iβ) was abolished using antisense oligodeoxynucleotides (ODN) against PKG Iβ (AS-PKG), dibutyryl-cAMP (db-cAMP, 3 mM) failed to decrease ICa(L). Furthermore, the expression of β subunit of L-type Ca2+ channel was abolished by antisense ODN against common sequence of β2a, β2b and β3, db-cAMP (3 mM) also failed to decrease ICa(L). Thus, β subunit of L-type Ca2+ channel may be necessary for inhibition of ICa(L) by cAMP/PKG Iβ cross-activation in VSM cells. To further explore the role of β subunit in regulation of L-type Ca2+ channel by phosphorylation, A7r5 cells were transfected with β2a cDNA/pcDNA3 or β3 cDNA /pRc/CMV expression vectors using lipofectamine and ICa(L) will be tested for further inhibition in the presence of FSK, db-cAMP or db-cGMP. [J Physiol Sci. 2007;57 Suppl:S235]
