Where is the inverting factor in hormone secretion from parathyroid
cells?.
Cohen, Yosef, Ruth Rahamimov, Tally Naveh-Many, Justin Silver, and
Rami Rahamimoff.
Department of Physiology and the Bernard Katz Minerva Center for
Cell Biophysics, Hebrew University Hadassah Medical School, Minerva
Center for Calcium and Bone Metabolism and the Nephrology Services,
Hadassah University Hospital, Jerusalem, Israel.
APStracts 4:0122E, 1997.
Secretion of hormones and transmitters in the body fall into two
general categories. In the majority of the secreting cells, including
the presynaptic terminals in the nervous system, an increase in the
extracellular calcium causes an increase in secretion (4, 9, 22, 23).
There are two notable exceptions to this general rule: the
parathyroid cells (3, 15) and the renal juxtaglomerular cells (5),
where an increase in extracellular calcium leads to a decrease in
secretion. Since these two cell types have a cardinal role in a wide
variety of physiological and pathophysiological functions, it is of
great importance to understand the regulation of their hormone
secretion process. A key element to such an understanding is the
identification of the location of the aeinverting stepae, which makes
the parathyroid cells behave in an opposite fashion to most other
secretory cells. Whole cell imaging studies strongly suggested that
the inversion factor is between the changes in intracellular calcium
concentration and the secretion of the hormone (24). Surprisingly,
confocal calcium imaging of the parathyroid cells did not support
this dogma. It reveals that the interior of the parathyroid cell is a
nonhomogeneous medium, and an increase in the extracellular calcium
concentration produces changes in [Ca++]in, both in the same and
opposite directions, in different parts of the parathyroid cell.
Received 1997 March 17; accepted in final form 1997 May 20
APS Manuscript Number E119-7.
Article publication pending Am. J. Physiol. (Endocrinol. Metab.).
ISSN 1080-4757 Copyright 1997 The American Physiological Society.
Published in APStracts on 11 June 1997