Diurnal expression of recoverin in the rat retina

The levels of expression of recoverin mRNA and protein was examined during a 24-h period in the rat retina. Northern blot analysis revealed that rat recoverin mRNA expression was consistently high during the light period, then decreased after onset of darkness, and gradually increased later during the dark period. The cyclic rhythm in recoverin protein expression was consistent with the cyclic rhythm in recoverin mRNA expression, insofar as recoverin mRNA and protein levels were lowest soon after lights off, and there was an increase in expression late in the dark period. These observations suggest that the rate of recoverin transcription may occur maximally during the period of greatest exposure to light, presumably when it is most needed by the photoreceptor to fulfill its role in visual transduction, then decreases at night, when high levels of expression are not required.