Abstract
In previous studies we determined that protein kinase C (PKC) and calcium are important intracellular regulators of neuronal angiotensin II (Ang II) binding sites. In the present study we investigated the effects of the protein kinase C (PKC) agonist phorbol esters (PE) and also a calcium ionophore (A23187) on the specific binding of [125I]Ang II to brain synaptosomes prepared from rats of different ages. The rationale was to determine whether the larae changes in the level of brain Ang II specific binding observed in different age rats are due to changes in the regulation of these sites by PKC or by calcium. The present data indicate no qualitative differences in the effects of PE or A23187 on [125I]Ang II specific binding to hypothalamic or brain stem synaptosomes, from either 2–5 or 70-day-old rats, i.e. the active PE TPA increased while A23187 decreased Ang II binding in all situations. Thus, the dramatic differences in brain Ang II specific binding seen with age appear not to be due to changes in regulation by PKC or calcium.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Baxter, C. L., Horvath, J. S., Duggin, G. G., and Tiller, D. J. 1980. Effect of age on specific angiotensin II-binding sites in rat brain. Endo. 106:995–999.
Cole, F. E., Blakesley, H. L., Graci, K. A., Frohlich, E. D. and MacPhee, A. A. 1980. Brain angiotensin II receptor affinty and capacity in SHR and WKY rat: effects of acute dietary changes in NaCl. Brain Res. 190:272–277.
Mann, J. F. E., Schiffrin, E. L., Schiller, P. W., Rascher, W., Boucher, R., and Genest, J. 1980. Central actions and brain receptor binding of angiotensin II: influence of sodium intake. Hypertension 2:437–443.
Jonklaas, J., and Buggy, J. 1985. Angiotensin-estrogen central interaction: localization and mechanism. Brain Res. 326:239–249.
Fregly, M. J., Rowland, N. E., Sumners, C., and Gordon, D. B. 1985. Reduced dipsogenic responsiveness to intracerebroventricularly administered angiotensin II in estrogen treated rats. Brain Res. 338:115–121.
Wilson, K. M., Sumners, C., Hathaway, S., and Fregly, M. J. 1986. Mineralocorticoids modulate central angiotensin II receptors in rats. Brain Res. 382:87–96.
King, S. J., Harding, J. W., and Moe, K. E. 1988. Elevated salt appetite and binding of angiotensin II in mineralocorticoid-treated rats. Brain Res. 448:140–149.
Singh, R., Husain, A., Ferrario, C. M., and Speth, R. C. 1982. Rat brain angiotensin II receptors: effects of intracerebroventricular angiotensin II infusion. Brain Res. 303:133–139.
Feldstein, J. B., Sumners, C., and Raizada, M. K. 1986. Sodium increases angiotensin II receptors in neuronal cultures from brains of normotensive and hypertensive rats. Brain Res. 370:265–272.
Sumners, C., Watkins, L. L., and Raizada, M. K. 1986. Sodium receptors mediated down-regulation of angiotensin II receptors in neuronal cultures. J. Neurochem. 47:1117–1126.
Sumners, C., Rueth, S. M., Crews, F. T., and Raizada, M. K. 1987. Protein kinase C agonists increase the expression of angiotensin II receptors in neuronal cultures. J. Neurochem. 48:1954–1961.
Sumners, C., Rueth, S. M., Myers, L. M., Kalberg, C. J., Crews, F. T., and Raizada, M. K. 1988. Phorbol ester induced upregulation of angiotensin II receptors in neuronal cultures: potentiation by a calcium ionophore. J. Neurochem. (in press)
Düsterdieck, G., and McElwee, G. 1971. Iodination of angiotensin II and purification of the labelled hormone, Pages 24–30,in Kirkham, K. E., and Hunter, W. M. (eds.) Radioimmunoassay Methods. Churchill-Livingston, London.
Sgaragli, G. P., Sen, I., Baba, A., Schulz, R. A., and Cooper, J. R. 1977. The mechanism of action of collagenase of the inhibition of release of acetylcholine from synaptosomal preparations. Brain Res. 134:113–123.
Lowry, O. H., Rosebrough, N. J., Farr, A. L., and Randall, R. J. 1951. Protein measurement with the Folin phenol reagent. J. Biol. Chem. 193:165–175.
Castagna, M. Y., Takai, K., Kaibuchi, K., Sano, K., Kikkawa, U., and Nishizuka, Y. 1982. Direct activation of calcium-activated phospholipid-dependent protein kinase by tumor-promoting phorbol esters. J. Biol. Chem. 257:7847–7851.
Gonates, N. K., Autilio-Gambetti, L., Gambetti, P., and Shafer, B. 1971. Morphological and biochemical changes in rat synaptosome fractions during neonatal development. J. Cell Biol. 51:484–498.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Myers, L.M., Raizada, M.K. & Sumners, C. Effects of phorbol esters and a calcium ionophore on angiotensin II binding in rat brain synaptosomes. Neurochem Res 14, 25–30 (1989). https://doi.org/10.1007/BF00969753
Accepted:
Issue Date:
DOI: https://doi.org/10.1007/BF00969753