Increased expression of growth hormone receptor mRNA and insulin-like growth factor-I mRNA in volume-overloaded hearts.
Recent results suggest that insulin-like growth factor-I (IGF-I) may be involved in the transition of a hemodynamic load into cardiac hypertrophy and that the expression of IGF-I seems to be coupled to increased wall stress. The present study investigated the role of growth hormone (GH) and IGF-I in myocardial hypertrophy induced by volume overload. An aortocaval fistula (ACF) was created in male Wistar rats, and experiments were performed 2, 4, and 7 days after the onset of volume overload. Right and left ventricular (RV and LV, respectively) myocardial expression of GH receptor mRNA and IGF-I mRNA were quantitated by a solution hybridization RNase protection assay. RV GH receptor mRNA content was elevated on the fourth and seventh days after the induction of the shunt, with peak levels (0.63 +/- 0.16 versus 0.14 +/- 0.03 amol/microgram DNA for the sham-operated animals; P < .01) after 4 days. Similarly, IGF-I mRNA was significantly increased in the RV of shunted animals (1.26 +/- 0.13 versus 0.56 +/- 0.05 amol/micrograms DNA; P < .01) 7 days after surgery. In the left ventricle, where systolic pressure was reduced in ACF rats, no differences could be detected in GH receptor and IGF-I mRNA content between ACF and sham-operated rats on any of the experimental days. There was no difference in the ratio of RV to LV weight during the experimental period. We have shown that the thin-walled right ventricle responds to volume overload with an increase of GH receptor mRNA content followed by elevated expression of IGF-I mRNA.(ABSTRACT TRUNCATED AT 250 WORDS)
Isgaard
J
J
Department of Internal Medicine, University of Göteborg, Sweden.
Wåhlander
H
H
Adams
M A
MA
Friberg
P
P
D000818:Animals; D015152:Blotting, Northern; D015870:Gene Expression; D006940:Hyperemia / Q000235:genetics*; D007334:Insulin-Like Growth Factor I / Q000235:genetics*; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D009693:Nucleic Acid Hybridization; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D017208:Rats, Wistar; D011986:Receptors, Somatotropin / Q000235:genetics*; D012260:Ribonucleases
D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D012260:Ribonucleases