Rats maintained on this diet demonstrated a dramatic reduction in amylase enzyme activity. This reduced level was evident through quantitation based on activity per mg gland protein, as well as on activity per gland wet weight. This was confirmed by the densitometric scanning of Western blots of sodium dodecyl sulphate-polyacrylamide gels of total parotid gland protein. Immune precipitation of enzyme activity from cell lysates showed that liquid-diet animals had lower levels of amylase than chow-fed controls. Isolation of poly (A+)-containing RNA followed by in vitro translation indicated that the steady-state level of amylase-specific mRNA had increased relative to the total mRNA pool. This outcome was also observed by dot-blot analysis of the cellular RNA using an amylase cDNA probe. Thus the regulation of amylase synthesis in rats maintained on liquid diets may take place at the level of protein translation, as well as of differential mRNA stability or gene transcription.
ASJC Scopus subject areas
- Cell Biology