Role of NO/cGMP in the cardioprotective effects of intrathecal morphine preconditioning against myocardial ischemia-reperfusion injury in rats / 中国药理学通报

Aim To investigate the role of NO/cGMP in the cardioprotective effects of intrathecal morphine preconditioning against myocardial ischemia-reperfu-sion injury in rats. Method 54 Male Sprague-Dawley Rats were used to establish the model of intrathecal catheter placement. The rats were randomly assigned to 9 groups. SHAM (sham group), CON (control, sa-line) , ITMP ( intrathecal morphine preconditioning, 3μg·kg-1 ) , L-NAME+ITMP ( NO synthetase inhibi-tor,L-NAME ) , ODQ + ITMP ( guanylate cyclase in-hibitor, ODQ ) , KT5823 + ITMP ( PKG inhibitor, KT5823),L-NAME,ODQ,KT5823,6ratsineach group. ITMP were produced by three cycles of 5 min intrathecal injection of morphine and 5 min intermis-sion before myocardial ischemia, CON were achieved by intrathecal injection of saline in the same way, L-NAME+ITMP, ODQ +ITMP, KT5823 +ITMP were prepared by intrathecally administering L-NAME ( 30 nmol), ODQ(11 nmol) and KT5823(20 pmol) 10 minutes prior to ITMP respectively, L-NAME, ODQ, KT5823 worked as the control of inhibitors themselves respectively without ITMP. Subsequently, all rats were subjected to 30 min of left coronary artery occlusion followed by 2 h of reperfusion except the SHAM group. Myocardial infarct size, as a percentage of the AAR, was determined by 2 , 3 , 5-triphenyltetrazolium stai-ning. Results Compared with CON, the volumes of IS and IS/AAR were reduced in ITMP ( P <0.01 );the protective effects of ITMP were abolished by pre-treatment with L-NAME, ODQ and KT5823 ( P <0.01 );Conclusions NO/cGMP might be involved in the cardioprotective effect of intrathecal morphine pre-conditioning against myocardial ischemia and reperfu-sion injury in rats.

Dendroaspis natriuretic peptide regulates the cardiac L-type Ca2+ channel activity by the phosphorylation of alpha1c proteins

Dendroaspis natriuretic peptide (DNP), a new member of the natriuretic peptide family, is structurally similar to atrial, brain, and C-type natriuretic peptides. However, the effects of DNP on the cardiac function are poorly defined. In the present study, we examined the effect of DNP on the cardiac L-type Ca2+ channels in rabbit ventricular myocytes. DNP inhibited the L-type Ca2+ current (ICa,L) in a concentration dependent manner with a IC50 of 25.5 nM, which was blocked by an inhibitor of protein kinase G (PKG), KT5823 (1 microM). DNP did not affect the voltage dependence of activation and inactivation of ICa,L. The alpha1c subunit of cardiac L-type Ca2+ channel proteins was phosphorylated by the treatment of DNP (1 microM), which was completely blocked by KT5823 (1 microM). Finally, DNP also caused the shortening of action potential duration in rabbit ventricular tissue by 22.3 +/- 4.2% of the control (n = 6), which was completely blocked by KT5823 (1 microM). These results clearly indicate that DNP inhibits the L-type Ca2+ channel activity by phosphorylating the Ca2+ channel protein via PKG activation.

Effects of lactoferrin on activity of PKG in spinal dorsal horn in a rat model of neuropathic pain / 中华麻醉学杂志

Objective To investigate the effects of lactoferrin on activity of PKG in spinal dorsal horn in a rat model of neuropathic pain(NP).Methods Thirty-two male SD rats weighing 200-250 g were randomly divided into4 groups(n = 8 each): sham operation group(group S),NP group,lactoferrin group and KT5823(an inhibitor of PKG)group.Neuropathic pain was produced by placing loosely constrictive ligatures around the common sciatic nerve in group NP,lactoferrin and KT5823,while the sciatic nerve was only exposed but not ligated in groupS.In group S and NP,normal saline 10 μl + 50% dimethyl sulfoxide(DMSO)10 μl were injected intrathecally.Lactoferrin 100 μg + 50% DMSO 10 μl were given intrathecally in group lactoferrin.Lactoferrin 100 μg + KT5823 10 μl were given intrathecally in group KT5823.The paw withdrawal latency(PWL)to a thermal nociceptive stimulus was measured every 30 min within 180 min after administration.The rats were then sacrificed and the spinal cord was removed.The activity of PKG in the spinal dorsal horn was determined by immunofluorescence.Results Compared with group NP and KT5823,the PWL was significantly prolonged after administration in group lactoferrin and the PKG activity was significantly increased in group lactoferrin(P ＜ 0.05).There was no significant difference in the parameters mentioned above between group NP and group KT5823(P ＞ 0.05).Conclusion Lactoferrin reduces NP by inhibiting the activity of PKG in spinal dorsal horn in rats.

Regulation of expression of cGMP-dependent protein kinase I_? by calcineurin in vascular smooth mucle cells proliferation / 北京大学学报(医学版)

Objective: To dicuss the regulation of expression of cGMP-dependent protein kinase I_? (PKG I_?) by calcineurin (CaN) in vascular smooth musle cells (VSMCs) proliferation. Methods: Cultured wistar rat aortic VSMCs were used as an experimental model. CaN was inhibited by its special inhibitor cyclosporin A (CsA). Phenylephrine (PE) was given to stimulate VSMCs to proliferate. All of cultured cells were divided into four groups:control group, 0.5 mg/L CsA group, 5 mg/L CsA group and 5 mg/L CsA+10 ?mol/L PE group. The mRNA and protein expressions were assayed by RT-PCR, immunocytochemistry and Western blot analysis. Results: The OD ratio of PKG I_? mRNA expression in 0.5 mg/L CsA group resembled that in the control group while that in 5 mg/L CsA group was significantly higher than that in the control group (P