Electron probe microanalysis of calcium release and magnesium uptake by endoplasmic reticulum in bee photoreceptors.
AUTOR(ES)
Baumann, O
RESUMO
Honey bee photoreceptors contain large sacs of endoplasmic reticulum (ER) that can be located unequivocally in freeze-dried cryosections. The elemental composition of the ER was determined by electron probe x-ray microanalysis and was visualized in high-resolution x-ray maps. In the ER of dark-adapted photoreceptors, the Ca concentration was 47.5 +/- 1.1 mmol/kg (dry weight) (mean +/- SEM). During a 3-sec nonsaturating light stimulus, approximately 50% of the Ca content was released from the ER. Light stimulation also caused a highly significant increase in the Mg content of the ER; the ratio of Mg uptake to Ca released was approximately 0.7. Our results show unambiguously that the ER is the source of Ca2+ release during cell stimulation and suggest that Mg2+ can nearly balance the charge movement of Ca2+.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=50889Documentos Relacionados
- Location of Calcium Within Bacillus Spores by Electron Probe X-Ray Microanalysis1
- Effects of extracellular calcium and of light adaptation on the response to dim light in honey bee drone photoreceptors.
- Sodium-calcium exchange in the outer segments of bovine rod photoreceptors.
- Distribution of calcium and other elements in cryosectioned Bacillus cereus T spores, determined by high-resolution scanning electron probe x-ray microanalysis.
- Cyclic GMP releases calcium from disc membranes of vertebrate photoreceptors.