M. Gallego et al., Restoration of cardiac transient outward potassium current by norepinephrine in diabetic rats, PFLUG ARCH, 441(1), 2000, pp. 102-107
In cardiac ventricle, the density of the transient outward potassium curren
t, I-to, is clearly related to sympathetic nervous system integrity. This s
ympathetic regulation of I-to expression may be greatly significant to the
genesis of cardiac complications of several diseases such us diabetes melli
tus. Autonomic neuropathy, including cardiac neuropathy, is a complication
of chronic diabetes. The objective of the present study was to identify the
possible role of cardiac sympathetic neuropathy in the reduction of I-to c
urrent density in diabetic ventricular myocardium. Thus, we employed the pa
tch-clamp technique to test whether I-to can be restored in diabetic myocyt
es incubated with norepinephrine. We also measured, using HPLC, the catecho
lamine content of the stellate ganglion, which is responsible for cardiac s
ympathetic innervation, in normal and diabetic animals. The main result of
the present study was to show that a 24-h incubation of diabetic cells with
norepinephrine restores I-to density to control values. The restoration of
I-to current density by norepinephrine suggests that the diabetes-induced
reduction of I-to is at least partially attributable to a reduced trophic e
ffect of norepinephrine on the expression of I-to.