EurekaMag.com logo
+ Translate

Concentrations of phosphatidylinositol 4,5-bisphosphate and inositol-1,4,5-trisphosphate within the distal segment of squid photoreceptors


, : Concentrations of phosphatidylinositol 4,5-bisphosphate and inositol-1,4,5-trisphosphate within the distal segment of squid photoreceptors. Visual Neuroscience 10(5): 921-929

Although inositol trisphosphate (InSP-3) is a key substance in phototransduction of invertebrate photoreceptors, its intracellular concentration remains unknown. The purpose of this study was to assay its concentration and the concentration of its precursor, phosphatidylinositol bisphosphate (PtdInsP-2), within squid photoreceptors. Rhabdomeric membranes were purified and their PtdInsP-2 content measured with a phosphate assay after the extracted phospholipids were deacylated and separated by ion-exchange chromatography. At least 75% of the total PtdInSP-2 found in the retinal homogenate was associated with the plasma membranes of the rhabdomeric microvilli, where PtdInSP-2 was 3.1 +- 0.7% of the total phospholipids, a level comparable to values published for rat brain. In terms of rhodopsin, microvillar membranes contained 3.7 +- 0.9 mol PtdInsP-2/mol rho. The InsP-3 content of living retinas was measured with a radioreceptor assay. The basal content of dark-adapted retinas was 0.15 +- 0.05 InsP-3/rho, equivalent to 30 +- 9 nmol/g tissue that is about twice that of rat brains. Flash illumination ( apprxeq 1ms in duration) that photoactivated 1% of rhodopsin increased the level about fivefold to 0.68 +- 0.22 InsP-3/rho. Corresponding decrease in PtdInsP-2 was undetectable as it was within measurement errors. For PtdInsP-2, the measured content corresponds to 5.6 +- 1.4 mM within the volume of rhabdomere. Maximal light-induced concentration of InsP-3 is calculated to be 1.2 +- 0.4 mM within the cytoplasm of the distal segment. Each photoactivated rhodopsin leads to the formation of ltoreq 500 InsP-3 molecules when measured 15 s after the flash. Thus, high concentration of InsP-3 in these cells is primarily due to restricted intracellular volumes rather than to high amplification by the enzyme cascade. The InsP-3 concentration within squid photoreceptors is the highest yet reported for any transducing cell and may indicate the involvement of relatively low affinity receptors or channels during invertebrate phototransduction.

(PDF 0-2 workdays service)

Order PDF Full Text

Close
Close

Not the article you are looking for?
Click here to order the paper you need


Accession: 008371743

PDF Full Text: Submit


Submit PDF Full Text

No spam - Every submission is manually reviewed

Submitted PDF Full Texts will always be free for everyone
(We only charge for PDFs that we need to acquire)

Select a PDF file:
Close
Close

Other references

Yuan, J.; Callahan, B. T.; Ricaurte, G. A., 2000: Effect of cytoplasmic and/or vesicular dopamine depletion on methamphetamine-induced neurotoxicity. The present studies sought to investigate the role of endogenous dopamine (DA) in methamphetamine (METH)-induced dopaminergic neurotoxicity while controlling for potential neuroprotective effects of hypothermia. In the first study, Swiss Webster m...

Dubuisson., 1905: Formation du vitellus dans l'oeuf des Tortues et des Batraciens. Compte Rendu de la Societe de Biologie Paris, 59 427

Uyeno K., 1969: On the plans of the dermatological radiology and soft ray treatment of tumors of the skin. Japanese Journal of Dermatology 79(3): 287-288

Novitsky, Vladimir; Mogilevsky, L.; Boshchenko, Y., 1994: HIV-infection in the South Region of Ukraine. TENTH INTERNATIONAL CONFERENCE ON AIDS, INTERNATIONAL CONFERENCE ON STD Tenth International Conference on AIDS and the International Conference on STD, Vol 1; The global challenge of AIDS: Together for the future : 1) 276

Tochilina S. V., 1991: Ecosystem analysis applied to mapping of the Oligocene of the Northwest Pacific. Pages 5-19 1991

Colleaux, Laurence; Villard, Laurent; Lossi, A. M.; Belougne, J.; Fontes, M., 1996: Physical and transcriptional mapping in Xcen-Xq213 in relation with XLMR disorders. European Journal of Human Genetics 4(SUPPL 1): 102

Grootenhuis, G., 1976: Studies of mastitis in ten groups of female offspring. Significant differences were found in average cell counts and in results of bacteriological and clinical examination of quarters for mastitis among daughter groups of 10 AI bulls in the Netherlands. The % of quarters with cell counts above 500 000...

Shaw, S. M., 2000: If our research is relevant, why is nobody listening?. The reasons for the lack of dialogue between leisure studies and other fields are identified. It is suggested that researchers in other fields are simply not aware of, or knowledgeable about the research conducted in this field, or its application...

Decorte, Bart L.; Harris, Constance M.; Harris, Thomas M., 1993: Synthesis of oligodeoxynucleotides bearing structurally defined adducts of carcinogens. Abstracts of Papers American Chemical Society 206(1-2): ORGN 27

Filipinyi, Z., 1968: The present problem of egg production and purchase. Although there has been a 39.4 per cent. increase in egg production throughout Hungary between 1963-1967 some 60 per cent. is still derived from private households. This has been unsatisfactory mainly because of the seasonal character of this form...