The effect of 12-O-tetradecanoylphorbol-13-acetate (TPA) and epidermal growth factor (EGF) on type-IV-procollagen (basement-membrane collagen) and laminin synthesis, turnover, and secretion was studied in human A431 squamous epidermoid carcinoma cells. Type-IV procollagen and laminin were biochemically and immunologically identified in the medium and cell extracts using immuno-precipitation followed by sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. EGF or TPA produced a sixfold increase in type-IV-procollagen and laminin secretion within 2 h; this was accompanied by a three- to fourfold increase in the levels of cell-associated type-IV procollagen and laminin, respectively. The level of type-IV-procollagen and laminin synthesis and secretion remained elevated for at least 16 h after the administration of either EGF or TPA. A combination of EGF and TPA was more effective than either agent alone in promoting the secretion of laminin but not of type-IV procollagen. EGF and/or TPA did not, however, produce a selective increase in the synthesis of collagen and laminin, since total protein synthesis was also increased to the same degree by these agents. As determined by labeling and chase studies, neither EGF nor TPA had any appreciable effect upon type-IV-procollagen or laminin degradation. These results indicate that the synthesis of components associated with the basement membrane in A431 cells (i.e., type-IV procollagen and laminin) can be rapidly modulated by EGF and a tumor promoter, i.e., TPA.(ABSTRACT TRUNCATED AT 250 WORDS)