Acta Physiologica Sinica

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1 , , 51 (2), Acta Physiologica Sinica (No ) 3 3, (, ) ( Ito), 28 d (H28, 6 h/ d), Ito ( pa/ pf, P < 0105), Ito 42 d ( H42), Ito Ito H42 ( ) mv ( ) mv, ( P < 0101) ; ( ) mv ( ) mv, ( P < 01001), Ito : ; ; ; ; : Q463,,,, [1,, ] ( Ito), 1 [2, 3 ],,, ( [3,4 ) Ito ], Ito, Ito, SD, 250 g, 3 : Tel : ; Fax : ; E2mail :

2 d (H28) 42 d (H42) 6 h, 3500 m 28 d 42 d,, [5 112 ] (30 mg/ kg),, (A) langendorff, ( 70 cm H 2 O) A 5 min, 50 mol/ L Ca % 1 % ( bovine serum albumin, BSA) A 5 min,,,, 250 mol/ L Ca % BSA A,, 10 min, 110 mmol/ L, 100 % O 2, 37 [6 113 ], (23 25 ),, (Olympus CK2, Japan),,, ml/ min (Nar2 ishige, Japan) 2 4 M (giga2seal),,, (whole2cell recording) Ag/ AgCl, (CEZ 2300, Nihon Kohden, Japan) 386 pclamp 516 (Axon Instuments, USA), A/ D D/ A (Axon TL21, USA) 1 khz, CoCl mmol/ L, TTX 20 mol/ L, clampfit 10 mv (10 ms) 114 A (mmol/ L) : NaCl 100, KCl 10, MgSO 4 5, KH 2 PO 4 112, taurine 10, glucose 10, MOPS 10, ph 712 (mmol/ L) : NaCl 137, KCl 514, MgCl 2 110, CaCl 2 118, HEPES 10, glucose 10, ph 714 (mmol/ L) : KCl 140, MgCl 2 2, EGTA 11, HEPES 10, K 2 ATP 5, CaCl 2 1, ph 712 ( TTX, ) ( collagenase type ) (BSA) HEPES EGTA K 2 ATP Sigma 115 pclamp Excel Origin 411 (Mi2 crocal, USA) x s x, t Ito Ito, TTX Ito, (prepulse) 15 ms (holding potential HP) - 80 mv - 20 mv, I Na ( HP - 60 mv, 10 mv, 250 ms, 50 mv ), 012 Hz [6 ],

3 2 : 189 H28 H42 Ito H28 Ito ( pa/ pf, n = 9) ( pa/ pf, n = 9) ( P < 0105, 1,2), H42 Ito ( pa/ pf) ( P > 0105) 2 Ito I2V Fig12 I2V relationship of Ito density in ventricular myocytes isolated from the rats after exposure to intermittent hypoxia for 28 days (H28) and 42 days (H42) A. Left ventricle. B. Right ventricle. 3 P < 0105 vs control, # P < 0105 vs H Ito [6 ], Ito, 2 ( I2V) Boltzman I/ I max = 1/ 1{ Exp [ (V2V1/ 2) / s]},, ( ) (V1/ 2) ( s),, H28, Ito s V1/ 2 H42 Ito, V1/ 2, ( 3) (V1/ 2) mv ( n = 11), mv ( n = 11), ( P < 0101), V1/ mv ( n = 10), mv ( n = 7), ( P < 01001)

4 Ito Fig13 Alteration in the steady2state activation and inactivation of Ito in rat ventricular myocytes after exposure to intermittent hypoxia ( IH) 213 Ito Ito Ito, [3,4 ],, H28 H42 4 Ito Fig14 Recovery kinetics of Ito in rat ventricular myocytes after exposure to intermittent hypoxia A. Control traces from a representative. B. Left ventricle. C. Right ventricle. Ito (500 ms), 011 Hz,, Ito ( 4) : H28 H42

5 2 : 191 ( ) ( n = 7), ( n = 10) ms ( n = 10) ( P > 0105) ; : ( n = 9), ( n = 10) ms( n = 8) ( P > 0105) 3 Ito, 28 d, Ito, 42 d, Ito, I2V, 28 d Ito,,, [8,9 ] Ito, [10, 11 Ito ], [4, ], [1, ], H42 Ito, 42, Ito, ( 6 8 mv),,,,,,,,, [1 ] Meerson FZ. Adaptation to intermittent hypoxia and its use for protecting the heart from stress and ischemic dam2 age. In : Meerson FZ, ed. Adaptive Protection of the Heart : Protecting Against Stress and Ischemic Damage. Florida : CRC Press, 1991, [2 ] Barry DM, Nerbonne JM. Myocardial potassium channels : Electrophysiological and molecular diversity. Ann Rev Physiol, 1996, 58 : [3 ] Zhou J ( ), Zhou ZN ( ). Progress of study on voltage dependent potassium channels in cardiomy2 ocytes. Life Sci ( ), 1995, 7 (4) : 4 7 (in Chinese with English abstract). [4 ] Giles WR, Clark RB, Braun AP. Ca 2 + 2independent transient outward current in mammalian heart. In : Morad M, Ebashi S, Trautwein W, eds. Molecular Physiology and Pharmacology of Cardiac Ion Channels and Trans2 porters. Netherlands : Kluwer, 1996, [5 ] Zhou J ( ), Tian M ( ), Zhou ZN ( ). Inhibition of transient outward potassium current in rat ventricular myocytes by propofol. Acta Physiol Sin ( ), 1997, 49 (1) : (in Chinese with English abstract). [6 ] Hamill OP, Marty A, Neher E, et al. Improved patch clamp techniques for high2resolution current recording from cells and cell2free membrane patches. Pfl gers Arch, 1981, 391 : [7 ] Zhou J ( ), Hao XM ( ), Wang ZM ( ), et al. Characterization of outward current in mouse ventricular myocytes. Acta Physiol Sin ( ), 1995, 47 (6) : (in Chinese with English abstract). [8 ] Ten Eick RE, Zang K, Harvey RD, et al. Enhanced functional expression of transient outward current in hyper2 trophied feline myocytes. Cardiovasc Drugs Ther, 1993, 7 :

6 [9 ] Lukas A, Antzelevitch C. Regional difference in electrophysiological response of canine ventricular epicardium and endocardium to ischemia. Circulation, 1993, 88 : [10 ] Tomita F, Basset AL, Myerburg RJ, et al. Diminished transient outward current in rat hypertrophied ventricular myocytes. Circ Res, 1994, 75 : [11 ] Lue WM, Boyden P. Abnormal electrical properties of myocytes from chronically infarcted canine heart : Alter2 ations in V max and the transient outward current. Circulation, 1992, 85 : Acta Physiologica Sinica Apr. 1999, 51 (2), EFFECTS OF INTERMITTENT HYPOXIA ON TRANSIENT OUTWARD CURRENT IN RAT VENTRICULAR MYOCYTES 3 ZHOU JUN, TIAN MING 3 3, ZHANG YI, ZHOU ZHAO2NIAN ( Shanghai Institute of Physiology, Chinese Academy of Sciences, Shanghai ) ABSTRACT To explore the ionic basis of the strengthening effect of intermittent hypoxic adapta2 tion ( IHA) on the electric stability of heart, the effects of intermittent hypoxia on the transient outward current ( Ito) in rat ventricular myocytes were investigated by using whole2cell patch2clamp recording techniques. After 282day ( H28) exposure (6 h/ d) to intermittent hypoxia, the density of Ito in the right, but not in the left, ventricular my2 ocytes was dramatically increased as compared with the normoxia control ( vs pa/ pf, P < 0105), while the Ito density of the myocytes isolated from both sides of ventricles in 422day2exposure group ( H42) did not show significant differ2 ence. Except for a more negative shift of the steady2state inactivation curves (half2inacti2 vation voltages : vs mv in the left ventricle and vs mv in the right ventricle) in the H42 group, all the other parame2 ters for activation, inactivation and recovery kinetics of Ito of each group remained un2 changed. It is speculated that the change in the current density of Ito may be responsible for the different hemodynamic responses of the ventricles to the early stage of hypoxia. The alteration in inactivation may participate in the cardioprotective effect of IHA. Key words : intermittent hypoxia ; transient outward current ; patch2clamp technique ; adaptation ; heart 3 This work was supported by National Natural Science Foundation of China (No ). 3 3 Present address : Institute of Anesthesiological Medicine, Xuzhou Medical College, Xuzhou Correspondence author. Tel : ; Fax : ; E2mail :