Objective: To observe the effect of heat shock on tropoelastin mRNA and protein expression in cultured human dermal fibroblasts and to elucidate the possible role of heat shock in the development of solar elastosis in human skin. Methods: Primary cultured human dermal fibroblasts were incubated in 43 ℃ water bath for 30 minutes, then returned to 37 ℃, 5%(volume fraction) CO 2 atmosphere normal culture condition. The cells were harvested at hour 24 and 48 after heat treatment respectively. Total RNA was extracted from cell lysis and tropoelastin mRNA level was measured by Northern blot assay. Tropoelastin protein level in cultured supernatant was measured by Western blot assay. Results: At hour 24 after heat treatment, the level of tropoelastin mRNA was enhanced to (163?12)% of control group (P