Correlation between endogenous igf-1 and the changes of cardiovascular system in resistance trained rats

Introduction

The study discussed the mechanism of IGF-1 action when the cardiovascular efficiency and structure in rats were changing.

Methods

The subjects were 60 SD rats and were randomly divided into five groups: the control group(n=12) and the swimming
2.4.6.8 weeks groups (n=12). After 24 hours at the last training, catheter was inserted into carotid artery then into left ventricular to investigate cardiac function(dP/dTmax, IP,T) by polygraph computer. At last, the heart was picked up for
the starth and segment organization. We got the concentration of IGF-1 in serum (sIGF-1) and in the ventricular(vIGF-1) through RIA. By computer myocardial morphometry, we observed the changes of the cross-section length (L) in cardiac muscle cells and the myocardial capillary numerical density(CD) and the myocardial capillary to fiber ratio(C/F). The protein consistence of myocardial cells was examined by Accura proteins quantitative determination.

Results

(1)The dP/dTmax/IP, T significantly increased during 8 weeks training (P<0.05). (2) After 6 weeks swimming train, heart coefficient and L,CD,C/F significantly increased（P<0.05）. (3) When the rats have been trained for 6 weeks, the level of sIGF-1 and heart homogenates(vIGF-1) were significantly increased（P<0.05）. But the levels of the both at the 8th-week decreased at the point of the control group (P>0.05). (4) There was a significant positive relativity between vIGF-1, L, dP/dTmax/IP, T and heart coefficient. However there is no correlation between sIGF-1 and these of parameters except for dP/dTmax/IP, T and CD in ventricle.

Discussion/ Conclusions

(1)Local myocardial IGF-1 have been shown to enlarge individual cardiac myofibers in experiment probably, but the sIGF-1 did not. (2) The concentration of sIGF-1 and vIGF-1 have been shown to improve heart contractility, but have no correlation with the diastolic function. (3) Incretion IGF-1(sIGF-1) may cooperate with self-endocrine IGF-1(vIGF-1) to stimulate proliferation of smooth muscle cells and construct side-branch circulation. (4) Hypertrophy myocardial cells may be fit the training load and machinery signal decreased gradually. The level of sIGF-1 and vIGF-1 decreased at the 8th-week and there may be a kind of adaptive reaction to regulate the synthesis and secretion of IGF-1.

References

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