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CHANGES IN MYOSIN ISOENZYMES COMPOSITION AND THE MAXIMUM SHORTENING VELOCITY IN HYPERTROPHIC LEFT VENTRICULAR MUSCLE OF RATS

L1u L1-Q1oNG, L1 YUN-XIA

laboratory of Cardiovascular Physiology，Hunan Medical University Changsha 410078)

Abstract

Changes in unloaded maximum shortening velocity (Vmax) and myosin isoenzymes (MI) composition of rat left ventricular muscle were examined in the 8一week or 16week Goldblatt hypertensive (H8，His)and hypertension- regressive rats (R8).The Vmax was estimated by extrapolation to zero afterload from the tension-velocity curve of left ventricular papillary muscle，while the Ml composition (VI，V 2 and V 3) was separated by polyacrylamide gel electrophoresis and determined by densitometry. The results showed that:(1)A slow age-dependent shift to V3 and a decrease in VmaX were observed in 16一and 24一week-old rats (S8，Sie)，in which VI/V3 ratio was decreased respectively by 38. 9%and 61.0%and VmaX was decreased respectively by 8. 3%and
13. 3%when compared with that of the 8-week-old rats (So).(2)There was a significant decrease in V1/V3 ratio and VmaX in 8-week (H8) and 1 6一week (H16)hypertension induced hypertrophic left ventricular muscle as evidenced by the fact that the V1/V3 ratio decreased by 84. 4%and 9 3. 5%and Vmax decreased by 33. 3%and 48. 3%in H8 and Hlo as compared with that of the control rats (So).(3)There was a partial recovery in Vm- and V,/V3 ratio in (R8)group rats.(4)The V,ax was positively correlated with the level of V, (r=0. 9215，PLO. 01)and negatively with the level of V3 (r=0. 9071，P<0. 01)as analyzed in all the six experimental groups of a total of 48 rats (So， S8，Sis，Hg，His，R8).In conclusion，a significant shift of the myosin isoenzymes towards low ATPase activity V3 might be the biochemical mechanism response ble，at least in part，for the decrease in maximum shortening velocity in the hypertrophic left ventricular muscle induced by pressure overload.

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Citing This Article：

L1u L1-Q1oNG, L1 YUN-XIA. CHANGES IN MYOSIN ISOENZYMES COMPOSITION AND THE MAXIMUM SHORTENING VELOCITY IN HYPERTROPHIC LEFT VENTRICULAR MUSCLE OF RATS. Acta Physiol Sin 1996; 48 (4): (in Chinese with English abstract).