Age-related changes in the noradrenergic pattern and receptor responses of the rat cardiovascular system after repeated microwave exposure.

In the present research the effect of repeated microwave exposure on the noradrenergic pattern by histofluorescence method and on receptor-mediated responses using alpha and beta agonists in myocardium and aorta of young-adult and aged rats was studied. Young-adult irradiated rats showed an increase in noradrenergic innervation more marked in myocardial tissue, while an increase in maximal response to the agonist was found only at aortic level. Aged stressed rats exhibited an increase in fluorescent fibres at atrial and aortic level, but in the atrial section this increase was found to be less evident than in young-adult animals. Functional data in aged rats revealed a more marked decrease in maximal response ratio (M.R.R.) of myocardial tissue than in young-adult rats, together with a noticeable decrease in maximal response at aortic level. These results indicate no direct correlation between morphological and functional data. Participation of both central and peripheral mechanisms is suggested.

Noradrenergic innervation and receptor responses of cardiovascular tissues from young and aged rats after acute microwave exposure.

Young and senescent rats were exposed to 2,450 GHz microwaves for 45' and the effects of this treatment on the noradrenergic pattern and beta-cardiac and alpha-aortic receptorial functions were evaluated. In young animals, an increase in noradrenergic innervation was observed, while no functional modification was shown. In aged rats the increase in fluorescent fibers was almost the same as that observed in young rats, but significant variations in functional responses were found. Both at atrial and ventricular levels responses to the beta-agonist isoprenaline were unmodified in their affinity indices, but showed a marked decrease in the maximal responses; by contrast the activity of noradrenaline on the aortic alpha-adrenoceptors showed a great increase in maximal response without changes in the pD2 values. These results suggest that the predominant effect of microwave exposure consists in an increase in the noradrenergic pattern, and this effect is not related to the functional modifications.

MCF-10A cells infected with the int-2 oncogene induce angiogenesis in the chick chorioallantoic membrane and in the rat mesentery.

A growing body of evidence demonstrates the relevant role of the int-2 (FGF-3) oncogene in human carcinomas. To investigate its angiogenic activity, the human epithelial mammary cell line MCF-10A was infected with a retroviral expression vector carrying the int-2 oncogene. Infected cells were entrapped in an alginate pellet and placed on the chorioallantoic membrane of chick embryos. After 7 days, a dense capillary network was found to grow toward the pellet, whereas parental cells did not show any angiogenic activity. Conditioned medium from int-2-infected cells was injected i.p. twice daily into rats over a period of 10 days. The mesentery of treated rats showed numerous small blood vessels originating from larger vascular arcades and growing through the stromal layer of the mesentery. In control experiments, neither medium for cell culture nor conditioned medium from parental cells was found to induce angiogenesis. In conclusion, the stimulation of blood vessel growth by int-2-infected cells suggests that the production of the int-2 protein is associated with the acquisition of the angiogenic phenotype.

Suramin inhibits bFGF-induced endothelial cell proliferation and angiogenesis in the chick chorioallantoic membrane.

The effects of suramin, an inhibitor of growth factor mitogenic activity, were evaluated on basic fibroblast growth factor (bFGF)-induced proliferation of bovine aortic endothelial cells and on angiogenesis in the chorioallantoic membrane (CAM) of chick embryos. The role of bFGF gene expression in endothelial cell growth was also investigated by using an antisense oligodeoxynucleotide to bFGF. The 4-fold increase in [3H]-thymidine uptake in endothelial cells in vitro upon stimulation with 10 ng ml-1 of bFGF was inhibited by suramin 300 micrograms ml-1. bFGF antisense oligomer (10 microM) reduced [3H]-thymidine incorporation in exponentially growing cells by 76%; this effect was reversed by bFGF 10 ng ml-1. In the CAM of chick embryos suramin 50 micrograms was a more potent inhibitor of angiogenesis than the combination of heparin 60 micrograms/hydrocortisone 50 micrograms; the mean value of the area with reduced vascularity was significantly larger in suramin-treated CAMs (2.4 cm2) than in heparin/hydrocortisone (0.6 cm2), while the reduction of vascular density was similar (- 35 and - 29% compared to controls, respectively), In conclusion, the effects of treatments with bFGF and bFGF antisense oligomer demonstrate that bFGF plays a relevant role in endothelial cell proliferation and may be the target of suramin since the drug is able to suppress basal and bFGF-induced endothelial cell growth; in addition to this, suramin is a more potent angiogenesis inhibitor in the CAM than the combination of heparin/hydrocortisone.