Abstract: 　Objective To study the expression of nitric oxide synthase (NOS)mRNA in the gonad of Oncamelania hu-pensis in different temperature. Methods The snails were cultured at temperature of 0℃ , 15 ℃and 25℃for 1 month. The total RNA of each group was extracted with the RNA extraction kit. A pair of degenerate primers was designed from conserved regions of mammalian NOSs, and the expression of NOS mRNA in the gonad was measured by means of reverse transcription polymerase chain reaction (RT-PCR). Results The target genes of NOS were detected in the gonad of snails. The level of expression of snail NOS mRNA in 25℃ group and 0℃group was significantly higher than that in the control group( P <0.01), there was no significant difference for the expression products between 15℃group and control group (P>0.05). Conclusion The designation of primers of the snails was validated. The impact of temperature on the expression of snail NOS mRNA was determined, which suggested that NO plays an important role in the physiological and pathological modulation.

Key words: temperature, Oncomelania hupensis, nitric oxide synthase (NOS), gene expression