Effect of Urea Upon Growth of Fibroblasts from Cardiac Explants in Tissue Culture

Abstract

It has been found recently that allantoin, a purine derivative occurring in maggots' secretions, stimulated the healing process in deep purulent wounds. 1 Another derivative, urea, was discovered to be more effective in bringing about the same results. 2 It was thought that, since urea may be obtained from allantoin by hydrolysis, the growth promoting effect of allantoin might be due to the urea and not to allantoin itself.

Fibroblasts from cardiac explants in tissue culture grew more abundantly in the presence of 0.5% allantoin than those in control cultures; although the growth increase was not sufficiently great to be of real significance. 3 It was deemed of interest to discover whether the simpler product, urea, would increase the growth of fibroblasts to a greater extent than did the allantoin and to this end the present experiment was devised and conducted.

All cultures were made by the cover-slip-hanging-drop method with the observance of aseptic precautions. All water was triply distilled in an all-glass pyrex apparatus. The plasma was obtained by centrifuging blood drawn, without the use of an anti-coagulant, from the wing veins of young hens. The embryo juice was made by extracting 7-day chick embryos in Tyrode solution (pH 7.5) containing 0.25% dextrose. For the test series, urea, in quantities sufficient for a final dilution of 0.5%, was added to an aliquot part of an adjusted Tyrode solution before the extraction of the embryos. This concentration of urea was chosen because it was the same as that of allantoin used in a previous experiment 3 and further because the 2% solution, as used in clinical treatment of deep wounds 2 was too toxic for the cultures. Heart tissue of 7-day chick embryos was planted in a mixture of equal parts of plasma and of embryo juice, the latter containing the urea.