Ia. Greenwood et al., Differential regulation of Ca (2+)-activated Cl- currents in rabbit arterial and portal vein smooth muscle cells by Ca2+-calmodulin-dependent kinase, J PHYSL LON, 534(2), 2001, pp. 395-408
1. Ca2+-activated chloride currents (I-Cl(Ca)) were recorded from smooth mu
scle cells isolated from rabbit pulmonary (PA) and coronary artery (CA) as
well as rabbit portal vein (PV). The characteristics and regulation by Ca2-calmodulin-dependent kinase II (CaMKII) were compared between the three ce
ll types.
2. In PA and CA myocytes dialysed and superfused with K+-free media, pipett
e solutions containing fixed levels of free Ca2+ in the range of 250 nM to
1 muM evoked well sustained, outwardly rectifying currents in about 90% of
cells. The CaMKII inhibitor KN -93 (5 al) increased the amplitude of I-Cl(C
a) in PA and CA myocytes. However, the threshold intracellular Ca2+ concent
ration for detecting this effect was different in the two arterial cell typ
es. KN-93 also enhanced the rate of activation of the time-dependent curren
t during depolarising steps, slowed the kinetics of the tail current follow
ing repolarisation, and induced a negative shift of the steady-state activa
tion curve.
3. In PA myocytes, the effects of KN-93 were not mirrored by its inactive a
nalogue KN-92 but were reproduced by the inclusion of autocamtide-2-related
CaMKII inhibitory peptide (ARIP) in the pipette solution. Cell dialysis wi
th constitutively active CaMKII (30 nM) significantly reduced I-Cl(Ca) evok
ed by 500 nM Ca2+.
4. In PV myocytes, I-Cl(Ca) was evoked by pipette solutions containing up t
o 1 muM free Ca2+ in less than 40% of cells. Application of KN-93 to cells
where I-Cl(Ca) was sustained produced a small inhibition (similar to 25 %)
of the current in 70% of the cells.
5. The present study shows that regulation of Ca2+-dependent Cl- channels b
y CaMKII differs between arterial and portal vein myocytes.