Basic fibroblast growth factor in the developing bovine heart

Abstract

Basic fibroblast growth factor (bFGF) has been implicated in the development of the heart and in the proliferation of cardiac myocytes [ 1,2 and reviewed in 31. Mammalian ventricular myocytes lose their ability to undergo mitosis soon after birth and subsequent repair of damaged myocardium is limited to scar formation and hypertrophy of existing myocytes. While both ventricular and atrial myocytes proliferate in the foetal period, there is controversy as to whether atrial myocytes retain mitotic potential in the adult and whether this can be activated given an appropriate stimulus [2,4]. Atrial myocytes are less differentiated than their ventricular counterparts and in the adult retain certain protein phenotypes characteristic of the foetal atria 151.bFGF inhibits terminal differentiation of skeletal muscle cells [6] while in isolated neonatal cardiac myocytes, bFGF and insulin-like growth factors stimulate DNA synthesis and myocyte proliferation [2]. Higher levels of bFGF have been reported in adult atrial than ventricular tissue in the chicken, bovine, rat and sheep heart [2] although there is uncertainty as to the absolute levels present in heart tissue and their precise cellular location.In the present study we have determined the levels of bFGF in the developing and adult bovine atrium and ventricle using two independent immunoassays. The first which was developed in this laboratory, was a sensitive competitive enzyme-linked immunoassay employing a polyclonal rabbit antibody raised against recombinant bovine bFGF. The assay which employed a goat anti-rabbit peroxidase conjugate was able to detect bFGF in tissue extracts down to levels of 0.1 ng/ml. The second assay was a dioimmunoassay (Amersham International plc. ) employing 125-iodine labelled recombinant bovine bFGF and a rabbit antisemm. Bound and unbound bFGF were separated by a donkey anti-rabbit semm coated onto magnetizable polymer particles. This assay was also sensitive to levels of 0.1 ng/ml.The antibodies utilised showed less than 0.01% cross reactivity in their respective assay systems with bovine recombinant acidic fibroblast growth factor.Bovine hearts from foetal animals aged 11 weeks to 40 weeks gestation (term), from neonates (4 weeks old) and adults were dissected into atria and ventricles immediately after death, frozen in liquid nitrogen and stored at -7OoC until assay. As the extraction procedure may influence the final recoveries of bFGF, two different extraction methods, one at acidic pH [ 71 and one at neutral pH [8] were employed. Table 1. bFGF levels in bovine atrium and ventricle Each value rmresents the mean of three determinations. bFGF (udkn muscle1 Age Atrium Ventricle 1 1 weeks gestation 62 1Foetal levels in both atrium and ventricle which ranged from 329 -650 Hg/kg were consistently higher than in the adult (182 -275 pg/kg; Table 1 ) . Levels in the foetal atria were also 20 -100% higher than in the foetal ventricle throughout gestation and in the neonate although this was reversed in the adult. There did not appear to be an...

Intracoronary administration of FGF-2: a computational model of myocardial deposition and retention

“…FGF-2 concentrations ranging from 6 to 13 g/kg of tissue were originally reported for the healthy adult bovine heart (70). However, a more recent study reported an average FGF-2 concentration of 228.5 g/kg of tissue (10), which suggests that the absolute concentration of endogenous FGF-2 present in the heart is considerably higher than previously estimated. As a result of this uncertainty, model predictions are presented for both low and high basal levels of FGF-2 (F o,basal ) within the myocardial tissue (6 and 228.5 g/kg of tissue, respectively).…”