Table 1. Concentration of VEGF in the conditioned media of A431 tumour cells.

Cell number	24 h	48 h
2.5 × 104	<0.4	1
5 × 104	2	4
105	8	16

A431 cells were seeded at the indicated density into 24-well plate in DMEM–10% FCS medium for 24 h. After washing, they were incubated in serum-free medium. At the indicated time, the media were collected. VEGF-A concentration was asessed by radio immunoassay as described in Materials and Methods. Values are in ng ml⁻¹. The limit of sensitivity of the assay was 0.4 ng ml⁻¹.